1987
Check the date code on the Remington Society of America here: http://remingtonsociety.com/rsa/questions/barrelcodes
Late 1926
Remington's website has what you are looking for.
Yes, that would be the Model 51 made in 380 and 32 auto.
The Remington Model 51 pistol was not made by Walther. Has nothing to do with Walther. See the link at the right for a reproduction manual. sales@countrygunsmith.net
http://stevespages.com/ipb-remington-51.html
32 ACP
It's an inspection mark. If your interested in more information about the Model 51 there is a survey currently being conducted for them on the Remington Society of America under current research.
What Model 51 pistol or a rifle and what model?
100 years (approx) sn pa20568
75-750 USD