This is a vintage Mavic 501 RD (or closely related 500 RD) small-flange rear hub, dating from the late 1970s to the late 1980s. It features Mavic's legendary, buttery-smooth sealed cartridge bearings and is complete with its original vintage Mavic France quick-release skewer.
The hub is threaded for a traditional spin-on freewheel (typically accepting up to 6- or 7-speed freewheels depending on the spacer configuration and axle spacing).