Minolta Battery Pack BP-90M brand_Velbon this is arguably more useful

this is arguably more useful

which works by the principles of electricity

This is a  pretty sophisticated meter with ten-point averaging and cine mode- plus a weirdly retro-futuristic LCD display that wraps around the viewing area

So it will autofocus in theory

Packaged by the same folks who cut Kodak Aerochome

Minolta Battery Pack BP-90M brand_Velbon this is arguably more usefulThe Minolta Battery Pack BP 90M couples to a Minolta MD 90 motor drive, which itself attaches to a Minolta Maxxum 9000 camera, providing drive speeds of up to 5 frames per second. Camera and motor drive are sold separately, but this BP 90M is in excellent condition almost unused and would definitely make a nice addition to any Minolta Maxxum 9000 stack.