Can someone help me to identify the difference between a reproduction and NOS SS1 center cap? Are there identifiers to lookout for on the inside of the cap?

Warren

 

The GM ones, have a small ring around them close to the wheel. The aftermarket one do not have.

 

The Thornton reproduction caps have the ring.

http://thorntonmusclecars.com/product/ssi-center-caps

Is there another way to tell the difference? The one I am looking at has inside the cap a logo with a W and then a D C above it followed by a code 9384. The next line has the part number 393796. Does this look like a GM part?

 

So does the Fusick centers. The Fusick centers are high-quality non china pieces with the proper casting with the lip. They come with the backers and fasteners. $40ea.
Be sure to put a coat of carnuba on them right away.

 

Well I may have found an NOS but I want to be sure that it is definitely not a reproduction piece. That's why I need to know what the differences are.

 

Isn't the Part Number stamped on the inside? I know my SSII bolt have it, not sure about SSI

 

The one I'm looking at that is supposed to be NOS has it but accurate reproductions can include it just like the original. I don't know if the Thornton (Fusick) reproduction cap has it. Maybe someone that has one can confirm this.

 

I have Thornton caps, their very nice. I do think the part number is inside, but their out in the shop and its raining. I can check tomorrow.

 

Would it be possible to post a photo of the inside of the Thornton cap?

 

I did some digging into the difference between the NOS and reproduction versions of the SS1 cap. The Thornton piece is quite accurate on the surface, however if you look at the inside of the cap the part number shown is 93796 but the correct NOS part number is 393796. Otherwise, the alphanumerics are identical. Just an FYI for those interested in this sort of thing.

I also assume that the piece Fusick sells is the same as what Thornton sells. I did not investigate this.