I'm glad someone said the difference between the 39a and a mountie. I picked up a 1953 39a and it came with a straight stock and a curved straight lever. Didn't know which model I had all the numbers match until I saw this post.
Generally, I think at one time or another most folks would call all of the straight stock 39A's a "Mountie", whether purely a "Mountie", 39M or CL. There were a fair number of changes to mountie's over the years. I've found lots of entertainment learning about my Marlins, and learn something new... quite often. So, summarizing what I've gleaned from other threads here and at RFC, from Brophy, and a little personal observation:
Straight stock 39A introduced in 1953, pictured (and apparently produced) with a 24" barrel (but described as 20"). In 1954 they were 20" barrels.
In 1957 the "Golden" was introduced, and the straight stock 20" barrel 39A's were "Golden 39A Mountie". The "Golden" was dropped in 1964 according to Brophy but then I've seen a 1965 (AA) with a "Golden 39A Mountie" mark.
The 1969 catalog was the last that showed a "39A Mountie".
Though not in the catalog, in 1970 a very small number of "Model 39M" rollmarked 'mounties' were produced, still with rounded finger lever.
In 1970 the Century Limited's appeared, and in '71 the Article II, all with octagonal barrels and square levers.
The Golden returned in the 1972 catalogs, but now as the "39M" rather than Mountie. Those "Golden 39M" 'mounties' showed round finger-levers, new folding buckhorn rear sights but the earlier round front sight hoods. In 1973 they got the new wide-scan front sight hoods (oddly still pictured with a round finger-lever on the 39M, but the square lever on the rare '73 only "39M Octagon"). From 1974 on the 39M 'mounties' are shown with the square levers.
The gas escape hole appeared on the upper left side of the receiver in 1979, and the inspection hole for cartridge(s) in the magazine appeared in 1987.
The last catalog offering the "Golden 39M" was 1987, and in 1988 the 39TDS, a straight stock with a 16 1/2" barrel, appeared. In 1988 the "S" designation appeared in conjunction with the new safeties. The 39TDS remained in the catalogs through 1995.
The final bits of trivia are that from '58 on hammer extension spurs were included, and in the early or mid-'70's the 'JM' hammer spur extensions gave way to similar spurs in varying (evolving?) styles. Brophy says that Marlin replaced the steel 3/8" scope mount with the newly developed weaver-like double dovetail mount in 1972, but catalogs seem to show the steel mount as late as '75.
There are mentions of a bunch of exceptions; someone with more information will chime in if I'm off very far, and I'll learn some more.
TMI?[/airtool covered it very well, the 39 carbine was also made during the sixtys but don't know if it fits in the Mountie category.
When they changed from the 39a to the golden they added the gold trigger and barrel scroll. I have a 57 mountie that says 39a and has the blued trigger but most 57s have the golden markings.