I'm bored, and trying to stay away from the crap my wife is watching on tv. So, I'll give you a few freebies:
H&R Topper - Older H&R date codes are not as straight-forward as they may seem. So, you have to go with an approximate year. For AM, it should be ~1978. (produced 1974-1981)
Western Field Double - You'll need to provide much more information, including photographs. The Western Field shotguns included models from nearly every manufacturer, and they sometimes used the same model numbers over again. For example, the Western Field "model 50" was a Browning-designed, Stevens-built pump shotgun ... and 20 years later, it was a re-badged Glennfield model 60 semi-auto .22.
Winchester Model 12 - 1960.
Winchester Model 270 - 1963-1973. Serial numbers were not sequential, so only Winchester can be more specific (if they even have the records).
Winchester Model 62 - That serial number indicates that it is actually a Model 62
A. - 1947. (That 'A' matters, if you are going to sell it or repair it. ...Same basic design, but with some important internal differences.)
Marlin 995SS - 1996.
Marlin 55 - That seems to be a non-compliant serial number. Are you sure there aren't any other letters or numbers in that serial number? Either way... the fact that it has a serial number indicates that it's likely a post-1968 shotgun. Prior to 1968, they didn't put serial numbers on very many of the 55s.
For the Rugers, go here:
http://www.ruger.com/service/productHistory.html