What effect does cartridge loading have on sound?

Thanks for your response. It's definitely not wood,it's a solid shiny black color, metal or plastic. The store that sold it to me got it on trade form the person they sold it to years ago, so I wouldn't completely dismiss the notion that it's a MC. What happens when you plug a MC into a MM input? Does it play at all? Play very quietly?
While it sounds good, it doesn't bowl me over with the things that analog is supposed to. Compared to my Dual, it has better resolution, much better bass, more spaciousness, but somehow also a glassiness and not quite natural sound. It isn't as continuous or coherent as it should be. Could this be the result of improper loading? Or a cartridge that needs replacing (the cartridge was a bonus - I didn't even know it had one until I picked up the unit, & I was told that it was old and may need replacing)?

Great ideas - If I tilt the arm up, it allows the cartridge to pivot side to side on its little arm. Putting a small jeweller's screwdriver within 1/4" of the cartridge causes it to swing toward the screwdriver. Moving the screwdriver away lets the cartridge swing back to its naturl position (the arm in its raised position is a little past vertical, so the sub-arm swings to the right).

Also, the cartridge has a big gold V in the front, with what looks like a figure 8 knot (square knot? I was never a boyscout) above the V. I was mistaken about it being labelled Souther. Souther is printed on the headshell above the cartridge.

The output is definitely lower than my Ortofon, and I had to bump the gain on my Pass pre-amp to high (I think a 10dB gain), but having done that, it's plenty loud.

Any more suggestions?