The one on the left looks like the one on my 71 LT1 and the same as on a 70 Corvette as well.
The one on the right I believe is a reproduction - the oem domes have a fillet at their base VS a distinct transition from a die edge.
I am going to assume the OEM 68 one doesn't have the brake fluid SAE J1703 spec on it - I don't remember whether the 69 one has the brake fluid spec on it.