Petr,

In the 1960s, STC (Standard Telephones and Cables) was part of ITT 
(International Telephone and Telegraph Corporation) so the two bottles are 
probably electrically similar.

I never worked in Valve Division, but if I recall correctly the initial figure 
4 indicates a tetrode or a beam tetrode. Figure 5 was used to indicate either a 
beam tetrode or a pentode. The 55 probably does refer to the maximum permitted 
anode dissipation in Watts. One or other B may refer to British manufacture or 
base but I am not sure.

Before applying power to the heaters, you do need to confirm the voltage 
required. I believe some of these devices were designed for substantially less 
than the traditional 6.3V.

I hope this helps.

73:
John F5VLF


On 07 Jul 2014, at 09:20, Petr Maly <[email protected]> wrote:Wake up

> Hello all
>  
> 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
>  
>  
>  
> <IMG_0701_resize.JPG>