I apology for the off-topic. However I know that this group is attended by very experienced gents, mainly from the UK.

I found these two tubes in the junk, see the attachment. I spent quite a while to search the whole Internet for some specs, in vain.

They are very similar to QB3/300, or TESLA’s RE125, same size, same socket. The only visible difference is the shape and material of the anode.

I think the number 55 in the designation could possibly be the anode dissipation.

The labels are:

STC 4B/55

ITT 4B/55/B

By some lucky chance does anybody have any information about them?

 

Thanks, 73, Petr, OK1FIG