Used Leica M6 Classic 35mm (0.72) Rangefinder Manual Focus Camera Body - Black

The M6 (1984-1998) has only two simple > < LED arrows in its finder for the meter. There is TTL ambient light metering, but no TTL flash control, no flash-ready bolt in the finder, and no central "OK" LED.
Subject to the differences between rangefinder and SLR cameras, the LEICA M6 works just like a Nikon FM, and the LEICA M6 TTL is similar to the NIKON FM2, minus the fast shutter speeds.
The M6 is a completely different world from the Nikon SLRs. They feel completely different: you can flick the buttery-smooth Leica shutter dial with utter confidence with just a fingertip, while the Nikons require a very strong push, or two fingers.
The M6 has a tiny shutter dial that is hard to turn while you're looking throughthe camera, and it turns in the wrong direction with respect to the meter arrows.

Compatibility

The LEICA M6 and M6 TTL are completely compatible with all LEICA M lenses ever made, and with a simple adapter, even with Leica screw-mount lenses made since 1930.
The only gotchas are the usual: it won't meter with HOLOGON 15mm f8, SUPER-ANGULON 21mm f/4 or f/3.4, or the ELMARIT-M 28mm f/2.8 up to serial number2314921. These lenses focus and work fine, but you'll need a hand-held light meter.
Collapsible lenses and lenses with finder optics for the M3 also work fine.