MOSSBERG 151M(A): Closed bolt tube fed semiauto. Operation, details of an unusual mechanism

I,m a sucker for old 22 caliber weapons. Got me by accident this beautiful Mossberg 151m, I believe model (a).
Love this rear tube fed semiautomatic , closed bolt rifle. I had no idea it existed, before I saw it in a gun shop.
I believe it was made in postwar 1940s.

People were more daring at the time, experimented with different mechanisms, systems.
I don,t like as much more modern cookie cutter plastic hideousness and lack of charisma.
This one is charismatic alright, imho.

It,s in a good condition, I disassembled it , inspected , made sure everything is smooth and operational . Evidently it only needs sear/ disconnect flat spring replacement.
Also it,s missing: 1)front sight hood- ordered. 2) rear barrel sight( will try to find )3) swivels - perhaps can live without them.

The stock seems in an original finish. I like it and will leave it alone.

There,s no good video that demonstrates the mechanism of this unique rifle. I hope I will fill the niche.