Course this only speculation but
what is the date code ?
[AD] it will look about like this thought the letter may be different.
next barrel length 22" or 24 " ( if 22" it may not have the swivel lock, and can turn thus damaging the magazine spring ,Don't ask how I know
)
C/F caliber should be 44/40
I have one circa 1979
[AE] that is one of 500....
Post the photo, and I can tell better if it is an earlier N/A run of Rim fires C/F's .