Apron shower head for 1980s arm. Not G1/2 nor G3/4 threaded

[William Cheyne]

I need to find an apron shower head which fits an 1980s arm. The thread on the arm is either 7/8th inch or possibly 15/16th inch. It is unfortunately neither g1/2 not g3/4 thread.

Can anybody give me a link to an apron shower head (my current one is 5 inch diameter) which will screw onto my old arm or an adapter which will convert the arm to a g1/2 or g3/4 size

 

[rpm]

Try converting those measurements to BSP size threads.