the listed serialnumbers are from the merlinbike.com site back in the 1990s. so no idea when they made the 140-3517 bikes. ;) there are some frames with receipt. please check them to classify yours. merlin has been founded in 1986. don't think the first frames have been made in 1988.
merlin mountain incl. helfrich & marin frames	merlin elevator incl. prototype (≈150 frames)	merlin newsboy incl. prototype (≈380 frames)	arctos machine works	one-off titanium (≈40 frames)
first prototype, helfrich, 1985, hydraulic press none (the earlymobile), gary helfrich, 1985, xy, nancy, usa none, gary helfrich, 1986, xy, xy, xy none, gary helfrich, 1986, large, xy, xy ... none?, 1987, medium, marin, xy, xy none?, 1987, medium, marin, paul, usa none?, 1987, medium, marin, david turner, usa none?, 1987, medium, marin, jim harlow, usa none, 1987, medium, marin, joshua, usa none, 1987, medium, michael, usa xy, fat chance cyclo-crosser, 198x, xy, xy 31, 1987, medium, noah, singapore 38, 1987, medium, ashok, switzerland 50, 1987, medium, carsten, netherlands 65, 1987, medium, ashok, switzerland 80, 1987, medium, ashok, switzerland 81, 1987, small, ross, usa 85, 1987, small, ex-jay, usa 86, 1987, small, justin, usa 87, 1987, medium, jim, canada 90, 1987, medium, hans, usa 93, 1987, medium, ashok, switzerland 100, 1987, medium, ashok, switzerland 153, 1987, large, bedrich, switzerland 154, 1987, large, ashok, switzerland 164, 02.11.1987 receipt, large, stefan, switzerland 186, 1987, 13.5", ashok, switzerland 190, 1988, 17", noah, singapore 192, 1988, 17", mike, usa 199, 1988, 17", tim, usa 211, 20.04.1988 receipt, medium, andrea, italy 213, 1988, medium, carsten, netherlands 21 (cyclocross), 10.07.1988, xy, jennifer, usa 250, 1988, medium, ex-eric, usa 296, 1988, 17", ashok, switzerland 301, 1988, 17", ashok, switzerland 342, 1988, 15", ashok, switzerland 371, 1988, medium, ex-jeff, usa 389, 09.09.1988, medium, ex-geoff, usa 446, 1988, medium, marc, germany 1343, 01.1990, 15", daniel, germany 1393, 1990, 17", luca, italy 2988, 1990 year welded, 13.5", ashok, switzerland 4362, 1991, 15", ashok, switzerland 6980, 1992, 13.5", ashok, switzerland 8508, 1993, 18.75", ex-ashok, switzerland 9187, 1993, 18.75", ex-ashok, switzerland ...	none, 1990, xy", ashok, switzerland ... 4192, 1991, 19", mathias, germany 4198, 1991, 19", rc mounts, ashok, switzerland 4208, 1991, 17", xy, germany 4212, 1991, 17", lucas, canada 4215, 1991, 17", javier, spain 4220, 1991, 17", shay, usa 4225, 1991, 17", nik, uk 4231, 1991, 17", ashok, switzerland 4238, 1991, 17", rc mounts, ashok, switzerland 4240, 1991, 17", xy, xy 4243, 1991, 17", xy, xy 4248, 1991, 17", ex-mike, japan 4243, 1991, 17", xy, xy 4250, 1991, 17", luca, italy 4254, 1991, 17", desmond, singapore 4271, 1991, 17", gary, usa 4276, 1991, 17", carsten, netherlands 4280, 1991, 17", andreas, germany xy, 1991, 19", andrea, italy xy, 1991, 17", steve, switzerland ...   merlin suspension incl. prototype (≈250 frames) xx1, 1992, xx", xy, xy xx2, 1992, xx", jeff, singapore xx1, 1994, xx", xy, xy ... s003, 1993, 19", rick, usa s004, 1993, 19", edric, singapore s008, 1993, 19", omero, italy s012, 1993, 19", craig, usa s039, 1993, 17", xy, uk s043, 1993, 17", xy, xy s057, 1993, xx", drew, uk s076, 1993, xx", xy, usa s077, 1993, 15", ashok, switzerland s090, 1993, 15", carsten, netherlands s102, 1993, xx"", xy, ex-usa s109, 1993, 15", ashok, switzerland s122, 1993, 17", luca, italy s142, 1993, 19", xy, xy s163, 1993, 17", lucas, usa s178, 1993, 17", ross, usa dano, 1993, 17", dan, usa ...   merlin xlm xm001, 1995, 17", ashok, switzerland xm166, 199x, 17", ruggero, italy xm0884, 1997, 16.25", ex-ashok, switzerland ...   merlin taiga nx0061, 1997, 15", ashok, switzerland ...   merlin various prototypes & customs xxx. 1987, merlin road, kris, usa ... xxx. 1987, merlin touring drum brakes & integral rack, ashok, switzerland ... none. 1988, merlin tandem, ashok, switzerland xxx. 1993, merlin mountain tandem, xy, xy ... 288. 1989, merlin monostay, ashok, switzerland ... 777, 1989, mongoose titanium john tomac signature, 17", paul, usa 787, 1989, mongoose titanium john tomac signature, 17", paul, usa 788, 1989, mongoose titanium john tomac signature, 17", paul, usa none, 1989, merlin mongoose, 19", ashok, switzerland 1591, 1989, merlin mongoose, 19", ashok, switzerland ... 3600, 1990, merlin ashley, xsmall, ashok, switzerland ... 4332, 1991, raleigh john tomac signature, 19", mike, uk 4436, 1991, raleigh john tomac signature, 19", paul, usa 4438, 1991, raleigh john tomac signature, 19", paul, usa 4455, 1991, raleigh john tomac signature, 19", eric, usa 4456, 1991, raleigh john tomac signature, 19", eric, usa 4461, 1991, raleigh john tomac signature, 19", paul, usa 4xxx, 1991, raleigh john tomac signature, 19", mike, usa 4xxx, 1991, raleigh john tomac signature, 19", noah, singapore ... salsa titanium, 199x, bendicht, switzerland salsa titanium, 199x, noah, singapore ... merlin mountain 9119 with newsboy downtube, 1993/97, allen, usa merlin mountain with newsboy downtube, 199x, allen, usa ... c101286, ca. 1997, merlin bmx 24", ashok, switzerland ... none, 1998, merlin mca, ashok, switzerland ... xxx. 2003, merlin 29er prototype, 17", ashok, switzerland ...	666, 1988, 17", one piece, rob, usa ... n0005, 1995, 19", two piece, carsten, netherlands n0006, 1995, 19", two piece, ashok, switzerland n005, 1995, 17", xy, usa n006, 1995, 17", one piece, august, switzerland n009, 1995, 15", one piece, hans, germany n011, 1995, 15", one piece, desmond, singapore n013, 1995, 17", one piece, xy, xy n014, 1995, 15", one piece, ashok, switzerland n017, 1995, 15", xy, usa n019, 1995, 15", xy, usa n020, 1995, 15", one piece, dario, italy n021, 1995, 17", one piece, xxx, usa n022, 1995, 17", one piece, christopher, germany n024, 1995, 19", xy, usa n029, 1995, 17", jens, germany n030, 1995, 17", one piece, xy, xy n032, 1995, 17", one piece, xy, germany n034, 1995, 17", one piece, xy, germany n037, 1995, 17", one piece, xy, switzerland n039, 1995, 17", one piece, xy, usa n044, 1995, 17", one piece, xy, usa n045, 1995, 17", one piece, walker, usa n046, 1995, 19", one piece, bernard, usa n047, 1995, 19", one piece, eddy, italy n052, 199x, 19", one piece, ex-matt, usa n053, 1995, 19", one piece, xy, switzerland n055, 1995, 19", one piece, geoff, usa n061, 1995, 19", one piece, pim, netherlands n064, 1995, 19", one piece, xy, singapore n068, 1995, 19", one piece, august, switzerland n069, 1995, 19", one piece, oliver, germany n075, 1995, 15", one piece, romuald, france n076, 1995, 15", one piece, ashok, switzerland n080, 1995, 15", one piece, shaun, usa n084, 1995, 15", one piece, noah, usa n087, 1995, 17", one piece, tj, usa n091, 1995, 17", one piece, ashok, switzerland n095, 1995, 17", one piece, xy, xy n099, 1995, 17", one piece, ex-andreas, germany n100, 1995, 17", one piece, xy, usa n101, 1995, 17", one piece, tj, usa n103, 1995, 17", one piece, david, france n105, 1995, 17", one piece, ghee chuan, singapore n108, 1995, 17", one piece, alessandro, italy n115, 1995, 17", one piece, mike, uk n118, 1995, 17", martin, usa n120, 1995, 17", two piece, xy, usa n122?, 1995, 17", xy, canada n122?, 1995, 15", two piece, xy, switzerland n125, 1995, 15", xy, xy n147, 1995, 17", two piece, xy, xy n150, 1995, 17", two piece, travis, usa n152, 1995, 19", two piece, ex-martin, usa n153, 1995, 19", two piece, kevin, usa n154, 1995, 19", two piece, xy, switzerland 13519, 1997, 15", two piece, ashok, switzerland 13715, 1997, 19", two piece, ronnie, usa 14716, 1997, 15", two piece, e., usa 14040, 1997, 19", two piece, marco, italy 14592, 1997, 17", two piece, fabian, germany 14718, 1998, 17", two piece, lorena, italy unregistered: nxx1, 1995, 17", one piece, mountain bike hall of fame, crested butte mt. heritage museum, usa nxx3, 1995, 15", one piece, xy, xy nxx4, 1995, 17", xxx piece, xy, xy specials: xxx. 199x, merlin newsboy tandem, jeff, usa	arctos machine bruce gordon rock 'n road, noah, singapore arctos machine bruce gordon road, 700c, raw, ashok, switzerland arctos machine mtb brushed, 199x, ashok, switzerland arctos machine mtb brushed, 199x, scott, usa arctos machine mtb oval tt polished, 199x, ashok, switzerland arctos machine mtb polished, 199x, ashok, switzerland arctos machine mtb fuck you, 199x, noah, singapore arctos machine mtb polished, 199x, stevan, usa arctos machine paragon machine works road, 700c, polished, 1992, ashok, switzerland arctos machine road 650c raw, ashok, switzerland arctos machine tandem, 1990, bicycle guide, 1990/04 arctos machine train hopping, 1991, ashok, switzerland arctos machine tandem, 199x, xy, usa ...	one-off mtb, brushed, 1990, noah, singapore one-off mtb, leni fried, 1991, ashok, switzerland one-off mtb, brushed, 1992, ashok, switzerland one-off sling-shot mtb, 1991, ashok, switzerland one-off mtb, leni fried, 1993, alex, germany one-off mtb, leni fried, 1996, jim, canada one-off mtb, 199x, xy 01, xy one-off mtb, 199x, xy 02, xy one-off mtb, leni fried, 199x, xy 05, xy one-off mtb, leni fried, 199x, 06, lawrence, usa ... one-off road, 650c, ballou honeytube, 1992, ashok, switzerland one-off road, 650c, softride, 199x, peter, usa one-off road, 700c, leni fried, richard karpay, 199x, ashok, switzerland one-off road, 700c, leni fried, 199x, ashok, switzerland one-off road, 700c, 199x, marcus, usa one-off road, 700c, leni fried, 199x, rick, usa ... one-off tandem, titandemonium, 1993, ej & rick, usa ... one-off trials wo seatpost, leni fried, 1988, ashok, switzerland one-off trials, 199x, jim trigonis, usa ... one-off small wheels, 1991, paul, usa one-off small wheels, moulton, 199x, xy, xy ... one-off kids, leni fried, 199x, ashok, switzerland ...
many thanks to every owner for their pictures! you got more pictures or more infos about the equipment, please contact me at newsboy at merlintitanium.com.