I have two vintage Hamiltons, both have a 987er grade but I am not sure about when they were made. The pages I have found so far weren't that clear. Maybe one of the specialists here can help out.
The first one is a Hamilton Endicott
Grad 987-F Serial: 436 642 9
I am not sure, all I found differs between 1940-42 and well this DB:
http://www.nawcc-ch149.com/db_resch/hamilton_506.html says even 1934 (but that can't be, as I know Hamilton built the Endicott since 1937, right?)
The second watch:
Grade 987A Serial: 0427092
I've seen no list with Grade 987A, so I have no idea. From the style of the dial I would say something around 1945-48.
Thanks for your time.