#1
Howdy - I've got an old Marshall Gold Back speaker laying around -
12"
8Ohm
70 watts RMS

And I was just wondering if I could try it out in my 6505+ 112. (Basically, I don't know what "Ohms" are, and I don't want to blow up my amp.) I couldn't care less about the speaker - I've been trying to sell it for a long time for practically nothing, to no avail.

I'm not expecting it to sound better than my Sheffield, but hey, it's worth a try, right?
#2
This here says your amp is 4/8/16 ohms switchable, so you could switch the speakers and set the ohms selector to 8 ohms.

#2 of the Orange TH30 Clique
Gear:
Orange TH30 Head
Orange PPC410 Cab
Ibanez ART500e
Cort KX5
Almansa 434 Cedro