The M33 is one model of the relatively simple, ejector-less single shot club rifles made by Schultz and Larsen. These are similar to the M24 and M58 the somewhat more recent M70 and M77 models, all of which are distinguished by the period during which they were made and sometimes only slight differences in stock design, barrel diameter, sight configuration, and trigger.
Below are some examples of either M24, M33, or M58 models. It's hard to know which is which from pictures alone.


As noted, these are similar to M70 and M77 models, which have heavier stocks are themselves are distinguished primarily by the trigger, with the latter having a somewhat more sophisticated trigger design. They had various sight configurations, probably barrel dimensions, too.
Below is an example of a M70 and below it a M77. The receivers have been D&T for scope bases. These models didn't have factory dovetails for either aperture or optics, using a receiver sight instead.
The various triggers used on the M24, M33, M58, M70, and M77 models include variations of those below.
The M24, M33, and M58 models would likely have a trigger similar to the one shown on the top left.
