Examples from
70 Dearborn shown below to help illustrate the details we're focusing on here. In these examples we have one example with P&O finish while the other is zinc dichromate
This is what I have at this point including the one Hopey posted below of the Oct 69 built example All shown in sequential order
0F11918x Projected build Oct 69 Can't clearly see the finish but the bolt finish appears to be different than the bracket suggesting IMHO that they are not P & O
0F02G1xxxxx Oct 27th 1969 build date
Mid Nov 69 build date
0F14121x Projected build Dec 69
0F14274x Projected build Dec 69
0F15166x Projected build Jan 70
0F16973x Real build date of March 16th 1970
Appears that zinc dicromate was used early and in the later months with P & O for the majority of the mid month builds at this time for Dearborn built sportroofs with the fold down option