Is this MG08 Serviceable?

I am new to this forum, and new (sort of) to the MG08, even though I grew up with one as a kid. My grandfather brought one home from WWI, given to his son (my dad) in 1952. My dad registered it during the 1968 amnesty program in the U.S. He died a few years ago, and now the sons are interested in getting it into operating condition. 1915 DWM. However, I believe it is might be a "dewat" (decommissioned "war trophy"). I may be using incorrect terminology, so please forgive me. The check lever ("shark fin" lever on right hand side behind the charging crank/handle) has been removed or cut off, and it would appear that the receiver's right side plate has been modified with a piece of steel welded over the area where the check lever once was. From what I understand, the check lever ("dead stop"?) is required to keep the crank from over-rotating. Without it, I presume full-auto will not work (crank would not rotate back and forth); do not know about semi-auto/single shot. I am uploading two photos. The modifications, assuming these are modifications, were done between 1918 (end of war) and 1952 (my dad made no modifications, but assumed it was operable if he ever could find an ammo belt for it). Can anyone confirm if this is a "dewat" and whether the BATF likely would agree that it is unserviceable per their current standards? Would it be possible to render it operable again (complying with all applicable laws, of course)? I don't know if, years ago, the BATF ever "signed off" as to unserviceable status, applying their standards, if any, at the time.
As a final note, other than my rank speculation and having looked at dozens of other MG08, MG08/15s and other Maxim-style machine gun photos and diagrams (all of which have an external check lever), there is no visible or operational reason to suspect this has been modified. The small plate shown in the RH receiver plate photo has "patina'd" to the same extent as the side plate, has serial number markings that appear to match the size/font of stamped numbers elsewhere, and the crank does NOT rotate freely all the way around, but stops where is seems like it should in a to and fro cocking and firing operation. Was it possible that in 1915 the Germans were manufacturing this MG08 with some sort of internal stop (possibly visible in top down photo), and not with an external check lever?
Thanks, all, and sorry if I posted this inquiry to the wrong thread. I invite the Admins to move this post to a better place, if they prefer. But, frankly, I was hoping to get Mark's attention, seeing how involved and knowledgeable he is with the MG08, on this board and others.