Marlin did make a Model 36, and I have one.
It's a full-size version of what we now call the Model 94, wherein the sliding bolt forms part of the side of the receiver. The 336, in contrast, has a cylindrical bolt riding in a round bore in the receiver.
My particular Model 36 is in .32 Special, and dates from 1949. The date of production is identified by a letter prefix to the serial number; for example, mine is D99xx. The next year will use "E", and so on. With such a low number, I suspect the numbering would start at "0001" at the beginning of each year with the new letter identifier. The "W" letter is a puzzle, because I don't think the 36 series went past about "E" or "F" dates, when the 336 replaced it in the Marlin line.
The 36 rifles are very well-made. I imagine that Marlin could either produce the round-bolt 336 less expensively, or the design was stronger, or both. Whatever, the 36 is still an extremely nice rifle, and you won't see one every time you go to the range or gunshow.