How to identify tube amp


I just received a pair of mono blocks that don’t have any branding or identification.  It didn’t come with tubes so I’m not sure what tubes to buy for it!  How do I identify who manufactured the amp and/or figure out what tubes to get for it?
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By weight. Different manufacturers used different transformers, so you could weigh it.

(I'm joking).

Take pictures and share them.
This begs the question if you just received them who/where did they come from? Did you purchase them? If so did the seller not identify the amps or give any details?