Pre-1964, and it directly relates to the material type and machining process that were used. 

The serial number is the easiest way to determine if it is a Pre-1964 or a Post-1963 production receiver frame.  S/N 2600011 was the last Pre-1964.  S/N 2700000 was the first Post-1963.  All serial numbers in the 2600012 – 2699999 were skipped (not used). 

In addition to the S/N, the physical configuration (location) of the screws used to assemble the receiver frame are noticeably different (see the attached pictures).

Pre-1964

Post-1963

Bert

Chief 3302 said
So Bert, I m still confused. My receiver looks like the pre 1964 but my 7 digit serial number starts with 3479xxx. The numbers dont jive with the picture.

Help(?)

Chief 3302   

You will need to send pictures of your Model 94 to me so that I can attempt to determine what is amiss.

Bert – [email protected]