Scott,
What it appears to be is this:
G50-05 LSD- 911 Carrera 2 & 911RS America---USA---since 1992 model
I'm may be wrong but research that ID #. Ideally, what you want would be G50\50 or G50\52 (they’re strongest, respectively). The ebay item appears to be a G50 but not a G50\50 or \52.
The seller maybe only listing the first 6 digits because there should be 12 digits (11 min). In addition, I would request a digital picture of the serial number before I paid for it to be certain it has all it's numbers.
The 12 digit serial number structure of G50xx, goes as follows:
eg: G5052 2 L xxxxx
G5001, G5002, G5003, etc. = transaxle type
The next digit indicates variations in that particular transaxle, eg., 0 = no differential, 1 = "normal" differential, 2 = ZF limited slip
The letter code designates the model year. H = 1987, J = 1988, K = 1989, L = 1990, M = 1991. The model year "letter" was omitted, as of 1992.
The last five digits designate the serial number of the specific gearbox in question.