Grease pencil marking on firewall

[Duncan and son]

Jason and I just bought our sixth 72 BB and it has very clear orignal grease pencil markings on the firewall. Long ago we figured the model no., engine trans, brakes etc but we have not been able to de-code the no. 6 that is usually in the center or the 2T or 4T that are both ends i.e. the first and last marks on the firewall. No imput on the no. 6. On the 2T & 4T some have suggested paint combinations but we have seen both on all paint combinations. Thanks Paul