At a guess a filament test?
To show a customer a valve works?
or maybe not!
How about an add-on amplifier to allow a crystal set to power a speaker?
Keith
An AF amp stage, by the look of the two transformers. There's just the right number of connectors for input, GB, output, HT and LT so I concur with Keith.
-Tony
I think that sounds feasible. But maybe for headphones otherwise since it needs a speaker it would have been built into a speaker cabinet.
No, not for a loudspeaker, just an AF amp and very probably for use with a crystal set (note magnifiers, they used to be known as)
-Tony
I don't know if for headphones or speaker but it does look like a note magnifier and don't forget few speakers would have been in cabinets as they would be of the Horn type.
It would probably drive a horn speaker from a crystal set for local stations.
The Brown colour of the Bakelite looks similar to the colour of the Bakelite base of some BTH C2 Horn speakers
A very nice looking item 
Have fun
Mike T
I don't care if it was a bargain whats it doing on my kitchen table. www.cossor.co.uk
