Bayoujim said
How many experimental m 12 16 ga did they make this one is 5582   

Why you think it is “experimental” ?  Winchester began regular production of the Model 1912 in 16-gauge late in the year 1912 but they did not advertise them until 1913.  I just recently looked at a serial number 3848, a 16-ga Model 1912.

Bert

Bayoujim said
Just going by my Dave riffle book he is showing only 20 ga. Offered in 1913 and also showed prototype 16 ga. So it’s a 1913 ?  

Dave Riffle did not get all of his information correct.  Serial number 5582 was applied in November 1912.  As I previously stated, Winchester began manufacturing 16-ga Model 1912 shotguns shortly after they started production of the Model 1912. Initially, they were just 20-ga guns, but the 16-ga was very quickly added to the production list.  The 12-ga guns were added in 1913.

Bert