except for michaels publication from 2004 i really couldn't find some helpfull info on the difference between these 2 watches. as i want one to add one to my collection i kindly ask for your expertise. is there any favorite between the two ?
tia michiel
only the production date
The original 3 digit reference numbers were changed in the 1970s to 4 digit numbers. Originally it was thought that the changeover occurred in 1974 but more recently there's evidence it occurred in 1971-2; I personally suspect that it was a "rolling" renumbering and not always done consistently.
Some models changed radically in reference number, and a few of the more recent ones basically had a 1 added to the beginning.
For the 812AD, as you presumably know the A means automatic and the D means date --and this model was only made as an automatic with date. So it was easy enough to drop the AD and add the 1 to make the designation four digits.
Regards,
Michael
P.S. By the way, some AD models didn't have those letters engraved on the inside casebacks.
thanks michael (nt)