Unknown mark studio pottery teapot

Hi everyone! I am new to this forum and have acquired a large collection of studio pottery American, British, Japanese etc. Most is well made. But after a lot of time researching I cant ID most of it. I know a little about pottery, but not sure of all the glaze techniques etc. I'll start it off with this nice teapot. Let me know if my pictures are alright. And I really appreciate any help! Thanks!!

try pressing clay or blutac into the mark to see if you get a clear imprint