Ken,
I will disagree with you. And there are a few reasons why.
We know that in mid 1944 that the ZF41 was designated a non-sniper or marksman rifle, what ever you want to call it. Production seems to stop around this same point. However, then we see production begin again in the late K block but mostly L block of 1944. So at this point why are they making them again? Typically I completely agree with you that the Germans would never issue a sniper rifle without numbering the scope mount. But as I mentioned they already decreed that the ZF41 was not a sniper rifle. So possibly they chose not to number the mounts for this reason. By this point they were also not numbering rear sight components on regular rifles. What is the difference? I suspect that it was not to import to number the mounts anyways if everything is properly assembled (if that makes sense).
Another reason for my belief is that we have a considerable amount of these L block and byf45 no letter block ZF41 rifles and yet I have never seen a matching mount example. Some claim to have pictures but they could very easily be fake. So many of these late ZF41 (as I call them) are in minty, un-issued condition that we should find them fairly regularly with matching mounts, don't you think? Yet none. And Mauser would have never wasted their time putting the sight bases on rifles without the intent of using them.
Also, why so many un-numbered mounts? While these are late rifles they are not the final months late. As a comparison, finding un-numbered G/K43 mounts is tough because they did number them until the very end and the un-numbered ones were captured at the factory. That is because the K43 was still considered a sniper rifle.
I am certainly open to being wrong. However, based on the all the rifles I've seen, logic tells me that they stopped numbering the mounts. Good pictures of a legit late ZF41 with a legit numbered mount would blow my theory to pieces. So if someone has one then please post it. I hope this all makes sense. Great discussion.
And FYI Xavier, I have seen several late ZF41 rifles with a fake e/135 proof added to the sight base. Be careful. Very easy thing to add. And not sure I would call it a "sniper proof." More then likely a inspection proof to show that the base was properly assembled.