Bertone quality control stamp?

[Coupefan]

I just ripped off the old upholstery off the rear bulkhead so I could add some soundproofing and new upholstery (see What Did You Do Today to Your X1/9) and I found this Bertone stamp. Anyone know the significance of it?

 

[twincam69]

I don't know the significance but there's one on the passenger side door of my '75 as well.