Model 1936: 1936 to 1941.
30-30, 32 Special
The 1936 had case colored receivers & Model 1936 on upper tang.
1936 1st series production (no letter prefix serial numbers) had flat mainspring, fluted comb buttstock, perch belly forearm, hard rubber buttplate w/slotted screws. Starting in 1937, this model was listed in Marlin's Catalogs as the Model 36 and was only there referred to as the 36. The gun itself was still stamped Model 1936 until sporting arms production was discontinued in 1941. Serial numbers located on the lower tang under the lever.
B-prefix series: Changes to unfluted comb & beavertail forearm, hard rubber buttplate w/ phillips screws, upper tang was shortened and the use of coil mainsprings vice leaf mainsprings. 1941 Production.
No Letter Prefix-1936 to 1940
B-1941
Would realy need to know what the serial number is and barrel address in order to narrow it down.