You could start with the Beitman's index or Sam's number. I've been meaning to add a page to my site about this, but...
Beitmans (1928-1965) online at
http://www.eskimo.com/~p0lez1/beitman/beitmanhome.htm
Download the index and check which volume it's in.
Sams index:
http://www.samswebsite.com/photofact/pf_search.asp
Darn! I lost the page which had a list of Sams number vs. year.
Also, check the caps (esp. electrolytic cans) for manufacturer date codes - usually in the form yyww like 5426 - June '54 (they often updated their stmps quarterly, so you'll see a lot of 13, 26, etc.)
My site:
http://www.audiophool.cjb.net