What have I found here?

New member here.  Electronics hobbyist who made a career out of live sound.

Curious if anyone here might have some insight on these two amps I recently purchased from an estate sale.  $20.00 for the pair.
Won't be plugging these in anytime soon.
What brought me to this forum were the Dynaco A-420 output transformers.
One amp does have a Mullard GZ34/5AR4 tube.  The other is a "Realistic" 5AR4.
Tung-Sol 5881's on the outputs.

Nice Find! I have no idea what they are but that "Realistic" 5AU4 may also be a Mullard.
I pulled a couple 12AU7s out of a Heathkit o-scope, branded Heathkit, but give the Mullard flash.
Regardless, a great project worth saving.
Let us know how it works out!

Looks like a nice pair of home brew amps. The Realistic 5AR4's may be the Japanese copy of that tube. I believe Hitachi made them. The glass envelope would have a crease across the top if they are the Japanese made 5AR4. They were a good quality tube. International Components (aka: International Servicemaster"), a former tube reseller from Long Island, used to sell them.

Thanks for the replies.

@tuberadios69.  Upon closer inspection, sure enough the Realistic tube does have Japan stamped on it.

Not sure what my next move will be on these.  For the moment they are on the shelf and in line for consideration of a rebuild.  I will post back when I make a decision.  As others have noted regarding parts and the current issues with sourcing items that used to be somewhat readily available.  It makes the decision even harder.