The 300T is a 300 watt triode with a mu of 16 and a maximum frequency of 60 MHz for full output. This Eimac triode was usable to 250 MHz and was first announced in February 1936. The first example is typical with caps on the plate and grid. The second example was made in 1935 and may have been developmental. They were eventually replaced by the 450TH and 450TL. All photos of this tube from advertisements and handbook articles have typical "top hat" plate caps and grids. One example of the 300T has been found with wires out the top and a cap out the grid.
Length = 11.50" Diameter = 4.75"
Max voltage = 4000
Max current = 300 ma
Fil voltage = 7.5
Fil current = 11 amps