The I.Meffert rifle is neither a Haenel M1900 nor a M1909 action, but merely another try to "modernize" the obsolescent M88. Meffert's gunsmith went great lengths to make and fit new bottom metal to a standard M88 action to convert it to a flush magazine, probably merely single-stack two- or three-shot.
The action lacks the earmarks of the competing Haenels. The most obvious is Haenel's gas flange on the bolt, sandwiched between cocking piece and striker nut. The attached photos show the M1900 on top and the improved M1909 action below. Haenel forged their receivers completely different from the M88 to acommodate a staggered-column 5-shot magazine. Note also the different boltstop-ejector arrangements of the Haenels and the guide rib of the M1909 bolt.

M1900 bottom metal, floorplate latch in triggerguard

M1909 mag floorplate with release button on the left side.