These long nosed airframes were originally built by Ikarus as the Ikarus B-4. Some information here:
http://www.letletlet-warplanes.com/2008/05/20/ikarus-blenheim-b-4-in-finland/But the story is even more complicated than that; Ikarus had obtained license only for the Mk. I and produced these. Once information about the Mk.IV became available, they asked the license for that variant but initially England refused. But that did not stop Ikarus, they started to design their own Mk. IV look alike based on available knowledge (photographs etc.) and later England also sold the real plans for the Mk. IV. These airframes, which were almost completed 1941 when Germany attacked, were designated as the Ikarus B-4 and have some features of Mk. I, some Yugoslav origin features and something from real Mk. IV as well. When finished in Finland these got some features from Finland like wooden propellers etc.
The identity of the BL-200 in the FAF museum is also still somewhat unclear. It is known that at least two Blenheims were replaced (BL-106 and BL-197) with completely new airframes during the service after the war to avoid the license fees. The strange thing in the history of the BL-200 is that after the war it was stored long time and then taken to the overhauls. After the overhauls it entered service as a zero flight time airframe. So the question here is what happened in the overhauls; it's possible that large part of the original airframe were replaced with new parts but so far definite documentation has not been found.
