Sounds like you have an A-100 or some small spinet. Do you have a full pedalboard? If not, it's one of the spinet types. If so, then you have an A-100 type.
Looks like a leslie?
Type opening the back of the speaker cabinet. DON'T TOUCH ANYTHING! If you see a cylinder-looking thingy at the bottom and tv-antenna-looking thingy at the top then you have a leslie. If you just see the cylinder at the bottom, it's still a leslie, just a 145 or 125 type, most likely. If you just have speakers, then it's just an amp.
If you're getting a good sound, leave it alone. That's just my opinion. If not, then try getting a leslie.
No switch? Is it just missing? That's what I'm guessing.