i have an all american pressure cooker/canner model 921. it was my mom's and i don't have the instruction manual. i have only been using it to do boiling water bath, but would like to do pressure canning now. it appears to not use a seal/gasket, though there is this white rubber ring thing that is here with the accessories. i couldn't figure it out. then in an ad for one online one of the features it touted was there was no gasket. i can't find an online owner's manual. anyone have this canner or know how to use it properly?