Zetor model numbers?

I was just wondering is there any logic to, or information to be gained from model numbers? e.g. 6711, 6911
I think that 11 and 18 as the last two indicate 2wd and 4wd but what about 40 , 45 etc?
???

11 was cabless, 18 was with cab, untill the 6911 then they didnt give cab and cabless different model numbers.
45 is 4wd, 48 is cab 4wd.
16 is halftrack, 17 is low center of gravity.
13 is narrow (orchard) 43 is orchard 4wd
23 is narrow crawler.
12 was only used for the 4712 because a french eau de cologne manufacturer claimed the rights on the type designation 4711.

cheers Renze.
so what about the 47, 57, 67 etc?

My 6711 has a Alexander Duncan cab. would these have gone from the Zetor factory/ importers to the Duncan factory and then sold with cab? or would someone have bought a 6711 and then bought a cab?

4, 5 or 6 was an indication of engine power, 7 was a generation number. starting with 2011, 3511, 4712, 5911,6011, 6211, 6320, 6321, 6441 and then the Proxima 85, proxima 90

Duncan's made the cabs in Aberdeen and shipped them to the dealers who then fitted them. They are still in business and sell spares for thier cabs. My 3 Zetors have these fitted and the 5511 has one of the their first saftey cab ptototypes.