In general, most factory Winchester engraved Model 21's do not have the inital's of the engraver on the gun. This includes Model 21's manufactured during the 'Production' era and 'Custom Shop' era.
CSMC manufactured model 21's do have the initals of the engraver at least on the one I have, on the side of the trigger guard at the reciever, its actually the first intial and last full name.
We recently researched a gun attributed to Nick Kusmit engraved Model 21 Pigeon Grade
http://www.model21shotgun.com/showthread.php?p=179#post179 with his initals on the gun. Information straight from Nick was that this gunwas not in his records. Cody records show that this gun left Winchester as a stock Field grade.
For more information from other Model 21 fans, you can Register on my website.-Dick