Distinguishing a Cam-Lock Cap

Millers Falls used two different sizes of cam-lock caps, 1-3/8inch with a casting number of ??? and the 1-5/8 inch with a casting number of 344. Regardless of the final finish on the cap, the same cap was used on the correct size. Most of the caps I have seen have the number covered from the japanning including all the 1-3/8 caps in my collection.  Visually you can tell the difference with Millers falls having a round center support in the cam lever and Stanley having a long curved top center support.

Functionally, a Millers Falls plane body works great with a Stanley cap or vise-versa. This is for anyone who wants to make sure they have the same manufacturer of both body and cap.  

Millers Falls and Stanley Lever Cap

In this picture the cap on the left is the Millers Fall and the cap on the right is a Stanley.  With both caps next to each other you can see the different shape of the center of the cam support.