Help with 811b driver

Hello everyone. I am new here, and am I glad to find this site. I just recently acquired a pair of model 19. One of the set was working wonderfully, but the other was not. The 811b horn has no output. I was told it could be the driver's diaphram. I took it out and saw a sticker with the number of 27-03-033952 driver. I couldn't find any info about this. Could any of you expert outhere give me a hand in deciphering this number. Thanks a bunch. Oh one more thing, is great plain audio still operating? I tried calling and email but no luck. Is there another place to get the replacement diaphram and how much do you think I should spend for one? Best,