Thanks @VasCrabb, It comes up in Device Manager as a "HID-compliant mouse", same as my actual mouse (so I have two of these entries under "Mice and other pointing devices").
I didn't know about the mouse provider settings...mouseprovider was set to auto. I tried raw, and the command line tells me it is not supported. Tried win32, and it didn't seem to help (but I have left it set)
I also found, under "Advanced options" and then "Input Options", there is Mouse listed, and it was set to Off. When I turn this on, then my mouse pointer acts "wonky"...when I try to use the mouse to move around the MAME menus, it is like the mouse pointer keeps returning to the same location...moves a bit and then "bounces back"...I am so confused. However, when I enter the game, and use the TAB menu to set the dial, I can move my actual mouse vertically to set it, and then the spinner works in-game. YAY! Except that my mouse doesn't work in the menu system. Can't have everything I suppose.
But I am a step closer.
BTW: I tried changing the mouseprovider back to auto. Mouse now again works properly in the MAME menu, but the spinner no longer works in-game.
Looks like two key settings I was missing. mouseprovider=win32, and Advanced Options->Input Options->Mouse=On.
Any idea why the mouse no longer works in the MAME menu screens? Maybe it is confused by the two inputs (spinner and mouse)?