Some good speaker sites are: know this is a old topic, but It addressed what I have to ask.
I found a Bassman 410 cabinet it has tolex, and the plate on the back has it's info, but i can't find out the date of this cabinet.
You'd have to judge from the cosmetics and other design features like handles to decide which decade it was made.
If the speaker dates to 1965 that just means the cab could not be an OLDER model than that.
They are said to be dual purpose guitar and bass speakers but if you want to use it as a bass cab I think I'd go with higher power capacity.
First thing to do is pick purpose, then power, then what impedance the the cab likes.
Once you know that then you can start speaker shopping.
There are a wide variety of speakers even within the same brand.
Before going there know that advances have been made in cab tuning and porting since these cabs were designed. So while you can load modern speakers it will still have a different tone from modern cabs with a horn.
The first thing to do before buying new speakers is decide what amp is going to be pushing them.
The Fender Bassman Ten is a stage-ready Silverface combo amp with four 10" speakers and 50 watts of pure, classic tone.
Yes, it's kinda big and yes, it's kinda heavy, but crank the gain on one of these no-frills master volume amps and you'll wonder why you don't see more of them on the touring circuit.
So I'd say, that my best guess is congratulations it is a 1968 cabinet loaded with Oxford speakers.