Yes, you are correct. I don't think I can edit my original post.
I don't have any, but I think you want RN8C4L, "R" prefix denotes round key bow while "E" means Eaton bow, see thumbnail attached.
Trying to help another collector out - he is looking for Yale EN8C4L blanks. The Ilco number is Y201, which I can find, but he would really prefer OEM.
Add to the fact that no keys were every uncut from the factory and none from after market sources. So all keys will have to be made.
The one on the left is from the early 70's, the one in question on the right. Note lack of keyway letter & slightly smaller size--both in length and size of bow.
I did find a little more about the Philadelphia Federal Reserve vault. In an application to the National Register of Historic Places...
One more thing to add as it not alway the lock problem as sometime alway the door or mount frame could be out of line. I have see this many time as everytime they said something wrong with the lock...
*** TAKING OFFERS OR TRADES ***
Update: Yale SD is no longer available. // Updated prices, see below:
American Lock 748 Padlock, New, No Box, 2 keys -- New Price: $60