you could check craigslist and purchase a tube tester for not a whole lot of money. If your dad had more tubes it would more than pay for itself.
WE 300B tubes
Not sure if this is the place, but I have (4) Western Electric 300B tubes. My dad was an amp design guy ( Ted Hammond from NYAL). I would like to sell them but I don’t know how to go about it as they are not tested- obviously I am aware of their value if they’re in good working condition.
Thanks