This is a very, very cool piece, a 'new old stock' Carrera 6 / 906 LSD (Limited Slip Differential) https://pbase.com/9146gt/image/160939513. Used by some early 911's, 904, 906, 911R and even the 910 race cars. This LSD is used in conjunction with Nadella Drive Axle Shafts which I'm now missing.

If by chance you have the intermediate drive flanges and a pair of the corresponding early Nadella shafts in good working order, please be sure and email me at AJSERRANO @ MSN dot COM. Thank you!