The HK-253 is a 100 watt high voltage rectifier made by Heintz and Kaufman. This type in about 1936 was designated the HK-253A as it had a "50 watt" base and the same tube with an "Industrial base" became the HK253-B. By 1946 the A and B may have been dropped as it isn't noted in the data sheets and the maximum ratings changed from 10000 PIV at 750 ma. Two versions of the tube are shown although the second tube is only marked as a 253 like the EIMAC tube. The HK-253-C was a different, larger tube.
Length = 8.75" Diameter = 2.50"
Max voltage = 15000 PIV
Max current = 350 ma, 3 amps peak
Fil voltage = 5
Fil current = 10 amps