I don't believe that is a serial number, but rather the part number for the 'claw'.
SunTour derailleurs will have a two-letter date code on the back of the parallelogram. That's as good as it gets.
http://velobase.com/ViewBrand.aspx?B...b-dac2d4abd9e6
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'75 Fuji S-10S bought new, 52k+ miles and still going!
'84 Univega Gran Tourismo
'84 Univega Viva Sport
'86 Miyata 710
'90 Schwinn Woodlands
Unknown brand MTB of questionable lineage aka 'Mutt Trail Bike'
Plus or minus a few others from time-to-time