I have had an AL-811H for almost 10 years now, the original tubes where old Taylors junky, burned up, grid resistors had fell off the sockets in the amp blah blah the amp was in a really sad but complete state. After cleaning up and repairing the amplifier (grounding the grids directly too) the last place I purchased 811A tubes from was D&C Electronics (FL), they were made in China, 10 tubes was like $200, like 10 years ago.
I sold/gave away all the extra new tubes, I am still running the 4 China made tubes from D&C. I used to run the amp hard to 800 watts, but after learning that slapping the F out of that Grid Current Meter wasn't good, I dialed it back to about 500-600 watts, and it has lasted nearly 10 years, still full output, and for 4 years I did almost all FT8 (carrier mode!). I think Ameritron may have gotten their tubes from them, same thing, unlabeled Generic China 811A's. I do not think D&C is still same business they have merged with Richardson, (rell.com) who is a supplier and rebuilder of tubes for the commercial market.