Bill,
I got a bit confused. When you talk about the suffix block, are you referring to the suffix letter after the serial number on the front of the receiver? If so, mine has the letter "B".
There are three stamps on the frame, can you tell me the significance of them on my gun? It looks like the first number is 135 and the second is 136.
I took another photo of the stamps that is more clear.
Eric
http://home.earthlink.net/~flyer/_uimages/proofmark.jpg