I want to thank everyone for contributing to this thread. I am sure the owner will find it interesting. Thanks again, Craig

: Jeff - looks like yours is older. The bridge number you noted
: 450617 is correct and the back number is 57706 in this one. They
: could have been made in the same year?
: A note about opening the back - this one is also very tight. I
: almost always regrind the opening notch on snap backs so they
: can be removed easily. You can see where this was done just
: below the serial number on this back. This one originally was
: all chewed up from openers that were not used properly plus a
: slot that was too small to get an opener into. I use a 25mm
: course sanding pad on a Dremel tool to do this - works great and
: only takes a couple of seconds to do. The angle is probably
: around 10 to 15 degrees. Had to do the same for the bezel - it
: had no notch at all. Craig

: :