This is also the earlier Meyer NY with the more rounded sidewalls. Here are Brian's notes on the mouthpiece. I also can not find any charts with a Meyer 11 listed, but the charts I have seen have a 9=. This should put a #11 at around. BUT- this piece is also very large, measures a tip opening of.115, with a very long facing curve of 25mm (like a tenor curve). I will take cues from you on this one. The Meyer NY 11 alto- the facing curve is not necessarily bad, just unusual. That tip opening is SO large, but with the extra-long curve, that is what is making it playable for you. If you did like the way it played and did not find it a struggle to play such a large tip opening, I don't think it's necessary to change it.
I just know I could never play something so large on alto! But that's me- if it worked for you, then that's ok. So I think we'd be safe with just the baffle and body clean-up, and going over the tip and tip rail to get rid of that small ding in the tip. The item "Meyer New York USA 11M Small Chamber alto sax mouthpiece" is in sale since Wednesday, April 4, 2018. This item is in the category "Musical Instruments & Gear\Wind & Woodwind\Parts & Accessories\Mouthpieces".The seller is "lfandwhenwerise" and is located in Philadelphia, Pennsylvania. This item can be shipped worldwide.