[ForSale-Swap] maybe a relay?

[Ray]

I have a black sealed vertical mount item, 3 in diameter, and 6Inches high. 
It is a plugin with 8 pins  (2 rows of 4).

It is manuf by Kurman Electric Co. Inc.  Manuf part number P255A and it also 
is marked
Signal Corps Stock number 4 TRY 30

anyone have any ideas?   a web search did not help with the part number but 
yielded a few hits on the company but no Joy

Ray