I am having a very difficult time identifying this thread. This part is a plug that I am trying to replace because the threads were stripped.
The best fit for pitch is 11 threads per inch (imperial), but the major thread diameter is 32mm. It does not appear to be tapered and the rubber seal would support this observation.
I have looked through many standard thread size charts and have been unable to locate a match. I thought BSPP-16 was close enough (at 33mm) but when I tried, the BSPP plug was too large to fit the associated female thread.