Congrats, my friend.

That's imo a very rare tube amp.

From what i know in the 1950s Pye were a very large company when electronics in Britain had received an enormous boost from military advances in the Second World war.
A company that could make valve VHF direction finding equipment accurate and stable enough to locate a U-boat in the Atlantic and reliable enough to survive 16 continuous hours operation in a piston engined aircraft could easily design and build an AF amplifier with a flat response from 2Hz to 160kHz once they had decided it was necessary.
The range of audio amplifiers that bore the "Pye, Cambridge" brand were each intened to be the very best products the company could manufacture in each class. The people who designed and built them had been involved with the military contracts and had the advantages of knowledge and equipment that were beyond the resources of the contemporary companies that we think of as the founders of "hi-fi".
Have fun.