I've had my M20 for over a decade. It's pretty tricked out, with a GemTech SOS40 suppressor as the main deal on it and I'm finally thinking of getting another just for the rail so I can have the last few accessories.
It's s/n WL140, so if 140 is available.
If not, my Witness 10mm, of late my more regular carry gun, has a "4849" in it's "name" - so that's a backup.
* 140 - or - 4849 *
Thanks for the 'site!