[Milsurplus] Tube question

[Ray Fantini]

Ok, its not strictly military but perhaps someone in the group can
answer this or at least point me in the right direction.
I have a "breadboard " radio that uses three tubes, They are all four
pin but unlike any four pin I have seen before. they have only one large
pin that is marked as being the plate, with the two filament and grid
being regular size pins. their is no locking key or anything like a WE
tube. what can these tubes be? I know their a triode but they do not
have a base like the 26 or 30 tubes I have dealt with in the past, can
they be those X-201 things?
Ray Fantini, KA3EKH