Besides the Diana 50, the Falke 80/90, various Airsporters and the Anschutz LG54 are there any other underlever tap loaders you folks know of?
The Falke seems a copy of the prewar design Airsporter; is the Diana 50 a copy of the Anschutz LG54, something else, or vice versa?
Before WW2, just about every quality manufacturer had these as their top-of-the-line models! Many sizes, stock configurations, and etc., and yes all were copies of the early BSA / Lincoln Jeffries design to some extent. The post-war Airsporter is actually quite different from these BTW.
The D50, Falke 80/90, and BSF S54 were the "big three" German post-war underlevers. The LG 54 is a rare "civvie" version of the famous Hakim trainer for the Egyptian military.
The D50 appears to be a fairly clean-sheet-of-paper design - the cocking linkage, ball-sear trigger, and use of heavy stamped parts sets it apart from its contemporaries. The pre-war DIana 30 military trainer has some similar details but was, I think, a bit smaller. The rare post-war Milbro G55 may be more directly related to that one.
Another interesting design is the "Tornado" manufactured in Hungary by FEG, sold under the "Relum" and "Telly" names. Made in two different sizes and at one point marketed heavily in the UK. A rather bizarre reincarnation of these was the "Mauser 300SL," marketed as a match rifle in the 90's!
The big 'un you left out is the immortal Webley Mk 3. This was a nearly dead-nuts copy of the pre-war Diana model 45, and was manufactured from the late 40's to the mid 70's. The things were so well-made that most of them seem to still be around! Very common discussion fodder on UK forums at least.
BSF S54 Match:
Webely Mk 3's: