I think it was a Zeiss Ziel 6 or maybe a Ziel 8. will be good if you have the chance to test this before you spend money for an original scope.
you can find it from time to time on egun or ebay germany but I fear it would not go under 300 euro in good condition. this scopes were very expensive pre war and hard to find.
I would look for a good mechanic who can made a second pair of front and rear feet like the one's you have with the Ziel 4. chance is very high that they were of the same model.