Good day,
I was made aware of this thread and don't want to owe you my opinion, although I cannot see the pictures in full size. However, I have read the previous posts and was able to make up my mind about it. First the maker: August Geiger in Kiel is a very well known maker of private purchase Kriegsmarine (but also children's) caps. If you are happy with the quality, why you don't keep it and replace the tally with a nice ship's KM cap tally? I can help you with that if you wish.
Your theory with the AHS-attending kid turning 18 drove a huge smile in my face - did you come up with this or the dealer? At the age of 18, a boy thinks of other things but fancy MHJ caps, which are not needed anymore in a few months when he joins the RAD. Plus, at the AHS the normal Fahrtenanzug was worn, so there wasn't really a need for a posh head dress. Also, at the AHS you didn't really want to stick out as special, but you understood yourselve as "one of the group", unless you had desire to become a General or Admiral one day. In general I have not seen personally ANY genuine MHJ stuff which relates to the furthest with AHS.
John Robinson does it exactly right in this fairly tricky subject of MHJ caps: stick with what you can prove. Consider: 20 years before the MHJ was founded, half of Germany's male youth (poor and rich!) wanted to be a sailor Imperial Navy. There were 10's of Thousands of caps like yours.
To the tally: I know of a private collector from the Frankfurt/M. area, who sold a 3/368 Lübben tally in about 2009/10. (I know it that precisely because I just came days too late to buy it off him.) However, I cannot read the Gefolgschafts-number on "your" Lübben cap - so it stays unresolved whether there's a possibility of being the very same tally.
Lübben is a fairly small town south of Berlin and although an area with lots of lakes and other waters I guess the MHJ groupings were fairly small. What I try to say: the Lübben tallies should not be encountered too often. Generally I rarely ever came across two tallies of the same unit in my 15 years I'm collecting MHJ tallies and photographs of these in wear.
To the eagle: nothing to worry about - there was a large number of MHJ units which did not comply with regulations! A white topped 2nd pattern cap should be fairly rare in any way: 2nd pattern tallies came in late 38, early 39 and as far as I remember the seasonal change of cap covers was suspended by RJF orders about 1940 - @ Gary: please help here - I'm not at home where I have my files.
It was common that unit's leaders allowed the wear of the eagle on the caps, despite being against regulation. It is a matter of fact that all these boys identified themselves with the "adult" sailors of the KM - this was the sole purpose of the MHJ! So why not to turn a blind eye to an eagle on a cap ...
Hope this was of any help. Most was said already.
Rgds
Daniel