You are absolutely correct. I wonder if there are any web pages that can give you a general idea of when your marlin was made.
So, does that mean you found the serial number?
I am assuming so, as Marlin serialized pretty much everything but some cheap rimfires (but even those had date codes).
The lack of a cross bolt safety means it's pre-83. More than likely, it was built in the late '70s.
There are many charts out there to help date a Marlin, such as
this one. But if you fall into a transition year, the charts rarely have all the details. (Such as '72s being out there with either, or both, a 72 prefix or 28; or some '69s having an AE prefix, even though the transition to numbers [69 in that case] was supposed to be done in '68; and more...)
You're not likely to have a transition rifle. But if you do, post what the prefix(es) is (are) and someone here can figure out what it (they) really is (are).
Check out Marlin Forum. I got a old one but I didn't know they were made clear
back in 64. For a while they made some 336s in 44mag before the 1894.
The "336-44 Magnum" was made in '64, as well as the "336-444 Magnum" (the first .444 Marlin, later to become the Model 444); but they were all marked as 336s.
A 336 barrel will work in an 1894, and vise versa. But I doubt that's the case here.