When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
They appear to be OEM wheels by the 17x9J 50 numbers. The 50 meaning 50mm offset which was factory sizing, the aftermarkets were a slightly different offset. Also look for a part number starting with 959 which is common prefix for GM wheels. I have original chrome ZR1's that have 9592880 on the back.
I agree with the "17x9J 50" marking being found on OEM versions however, at least for the '98-'99 years, the OEM silver painted ZR1 style SS wheels had an embossed "GM" logo on the face between the spokes. I can't remember for certain if this same GM marking was present on the '96-'97 issued versions.
I do agree that the 9" wide, 50mm offset version is usually OEM, as the vast majority of aftermarket versions used the C4 Corvette sizing of 9.5" wide, 56mm offset. However, there was a time (~15 years ago) when the OEM SS sizing of 17x9, 50mm offset was available in aftermarket reproduction.
The spoke design and extent of lip polishing would also suggest either an OEM wheel or an older reproduction (newer versions use a slightly more squared off spoke and typically have a greater surface area of the lip polished).
The chrome version mentioned by Z28_6spd above was a slightly different situation; these were optional Y2Y content via SLP, but not offered directly by GM off the assembly line. So you could order the car new with them, but it was supplemental SLP content and I don't seem to recall those versions having the embossed GM logo.
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Slideshow: From wobbling harmonic balancers to failed EBCMs, these are the issues that define long-term C5 ownership and what repairs typically involve.
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Slideshow: A modern Camaro transformed into a retro icon, this limited-run "Bandit" build blends nostalgia with brute force in a way few revivals manage.
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Slideshow: Cadillac didn't just crash the high-performance luxury vehicle party, it showed up loud, supercharged, and occasionally a little unhinged...
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Slideshow: A one-off sports car that looks like a vintage Italian exotic-but hides a C6 Corvette underneath-just sold for the price of a new mid-engine Corvette.
Are these OEM? 
