Steve ol buddy. I'm not a Winchester expert, but from the little research I did in the mighty Rules book, this is what I've concluded:
All national match rifles had clip slots: Page 181
As Rule states, "Special Action Note, Clip-Slotting. All National matches were slotted for loading with a clip, regardless of the era or production period".
If your rifle was truly made in 1946, it will have the Marksman stock #2 or #3, depending on how late in '46 it was built. It will have the upside down "T" on the trigger, as all the target rifles had this.
It will have a full floating 24" std wt barrel, chambered in 30-06. There was, however, the option of the 308 win from 1953-1955 (According to Rule).
The 1946 is considered a "pre war" or type 1. Even though it was produced after the war, which can be misleading, which should have a clover leaf tang, type 1 wing safety, solid bolt knob, and no holes drilled in the rear bridge.
A 1946 National Match rifle would be furnished with a Lyman 77 front sight, which was a detachable type.
The rear sight was a Lyman 48WH and the stock was more than likely inletted for this sight.
