I just visited the the Mason & Hamlin website's page for serial numbers. They say "On a Model A or Model BB grand piano look into the piano at the plate, to the left of center. The four or five digit serial number should stamped on the plate, underneath the letters "A" or "BB", depending which model you have."

First, my plate does not have a serial number stamp - is that unusual?

The only serial number I find is one written by the rebuilder in magic marker upon the front of the keyframe. Based upon that number, the piano seems to be one of the last built in 1913.

Another question: There is a letter "A" stamped on the plate, near the termination of the longest string. It has some additional characters under the "A", it looks like this:

A
x
3

Does anyone have any ideas what "x 3" might mean?

Thanks.

If the piano was rebuilt, the plate may have been refinished and the serial number was not replaced. That seems to be the only place where the serial number is. There is usually a number which is somewhat close that is stamped on various parts, like the bottom of the music desk, but it is not the actual serial number. I wish people would be more careful with serial numbers!

The A x 3 is the version of the plate. There have been a number of minor variations to Mason & Hamlins over the years, but I do not know what they mean. They do not seem to be chronological, and I do not think that there is an absolute correspondence to those numbers and changes in the plate design.

whippen...my 1919 "A" has Ax6 out at the tail...mine does have the serial# stamped into the bottom of the case just below the keys, right in the middle, along with another short number. I've also seen it inside the piano, I think on the bed frame or action or both. Here's a pic on the harp.

Model & #

Sometimes the serial number is stamped onto the bottom of the keybed.

Not only serial #'s but case #'s....the case # is always different than the serial #, and is usually stamped in various places on the case...at least this is the 'case' with Mason & Hamlins.