First, Ruger never gives out production figures.
That said, the RENE has some info.
Some are marked with O.H.P. (approximately 1300) & some are not (approximately 300).
A slightly longer stock, M1 Carbine style sling mount, fiberglass handguard, red rubber recoil pad, & a oiler in the buttstock. Some are stamped with the last 3 digits of the serial number on the bottom of the grip. Known serial number range of 181-0xxxx and 181-47568 to 181-51296.
Kinda rare.