ETKA reference S743/S711 against 200/5000 series

[mark schofield]

Came across the reference S743/S711 against part no. 441 513 31 B
(gas filled shock absorber) when trying to sort out a suitable shock
absorber for 1987 5000 series Quattro Avant.
(The one that no one does a replacement for, yes I know). Local stockist has
actually supplied me with a Boge item that according to his invoice
corresponds to the above Audi reference although its no good for my purposes
(lowers 30mm, M12 rather than M10).
Anyone know what the reference S743/S711 is - just curious as to what this
model is?
All the dampers referenced have part nos. commencing 441, 443 and 445 - if
the first 2 digits are the model, what doe the 3rd digit mean?
Thanks
Mark Schofield