Determining the serial number of an UZI and if it's open/closed bolt.

[Etraveller]

Hi.
On a Mini UZI I saw, the numbers on the frame were for example 190884x, which was stamped in at least three places on the left of the (receiver & cover).

However in another place was stamped with the same digits preceded by the letter M, i.e. M190884x

Which one is the actual serial number, and if it is the one with the M, what does it mean?

And how does one determine if the Mini Uzi fires in open/closed bolt?

 

[4V50 Gary]

Cock it back. If it stays back on a non-empty magazine, it's open bolt. If it goes forward and chambers a round, it's closed bolt.

 

[MDW Guns]

Mini UZI are all closed bolt!