Have a friend that broke the fireing pin in his 39a  found one at midway for post 74 model cant seem to find anywhere to tell if his is post 74 or pre 74.  Here is what i know...    Marlin 39A     ser.  20296424   looks like possibly a "jm" stamped on barrel left side just in front of reciever...        however on some models there is a mechanical safty in front of the hammer on this one there is not.  Any information would be great.   Thank you.  The forms are a great place for info!

I broke the firing pin on mine years ago and sent a letter to Marlin they sent me the pin at no charge.

hm according to the info From : http://oldguns.net/sn_php/marlinlookup.php
I'd guess that it's pre-74 but that's just a guess. Given that your serial number
doesn't look like it would indicate a date, it looks to me like it would be pre-69

*edit*: well, in reading closer.. maybe not. I noticed what  put in bold below...

MARLINS MADE 1948 and LATER
Marlin Model 336 and Models 39-A and 39-M manufactured from 1948 to 1968:
A one or two letter code was used to designate the year of manufacture.

All Marlins (except lever action) manufactured from 1962-1968
A two letter code was used to designate month and year of manufacture.

All Marlins manufactured from 1969 to 1990:
The first two digits of the serial number designate the year of manufacture, either as the last two digits of the year (in 1969-71) or as a number code (1971 and later)..

Steve thanks for the info went to the sight if I understand it right then the gun in question was made in 1980.... but do to the fact that theere isn't a button safty on it I was guessing it to be older. Again thank you.

Just in case anyone else is interested found on web that the button safty was added in 1983. I was guessing that it would have been made mandidtory before then.