IBM mixmaster

I picked up carbine #6 recently.  It's an IBM import-marked mixmaster, s/n 38620XX, with the following:

undated IBM barrel with 'FED ORD INC  SO El MONTE CA' on the right side of the barrel just aft of the front sight.  The 'FED ORD INC' part is lightly struck and barely legible, the 'SO EL MONTE CA' a little more so.  There is a small 'P' proof mark lower down on the barrel, no other markings that I can see.  The barrel crown is flat and chamfered.  Barrel gauges .3020+ at the muzzle, and bolt does not close on a .30 carbine field gauge.

unmarked (as far as I can see, other than 'I.B.M. CORP. (over) 38620XX' under the rear sight and 'U.S. CARBINE (over) CAL .30 M 1' on the forward collar) receiver with 45 degree firing pin cut and extra cut on the bottom

Type III recoil plate marked D. I.

M2 potbelly stock - no external markings visible except what looks like 2 rectangles, each approx, 1.5 x 0.5 inches, stacked one on top of the other, lightly carved on the right side of the stock approx. 1 inch in front of the oiler cutout, 'VS' marked in the slide well on left side of barrel channel, 'Z' under the butt plate above the screw hole, and '3689942' stamped on the grip just behind the recoil plate.  Any ideas as to the significance of the '3689942' on the top of the grip?  I'm thinking it's a serial number (would be another IBM) showing that this stock was once paired with that action, and things got swapped around sometime in the distant past.  If so, which organizations/armies/countries were marking their stocks with the serial number?

2-rivet shallow-groove handguard marked 'TN'

cast (?) 'slope only' front sight marked 'RIA' on left side

adjustable stamped rear sight marked 'I. R. Co. (over) 7160060' on right side

Type III barrel band marked 'J.M.O.' (band) and 'EM-Q' (lug)

milled M1 trigger housing marked 'N (over) 9' on left side, no other markings visible

Type III mag catch marked 'CC (over) M'

Type IV rotary safety marked with 'stylized S in circle'

Type III straight hammer marked 'WM' on the left side

Type II sear with hole marked 'W'

Type II trigger marked 'R.I.'

Carbine Club Type E279A slide marked 'S'G'' (S prime G prime) in the inside bottom of the slide box

Type I slide stop with short spring

Flat bolt marked 'OI (inside circle)' on right lug.

Type III extractor marked '(dot)U' on inside

Type III firing pin marked 'SG'

There was no sling or oiler.

I bought this gun mainly because I didn't have an IBM already.  I was a little disappointed that it was import-marked, but the import marks are so faint that I didn't even see them when I first looked at the gun.  I'm debating whether to spend money to replace the obvious rebuild-added parts or save the money for another carbine from a manufacturer I don't yet have (Winchester, Underwood, Saginaw SG, Rock-Ola, Quality Hardware or Standard Products) - I'm leaning towards the latter.  Big problem - too many carbines left to get, not enough money.

Scott

Here is the mystery number stamped into the top of the grip of my IBM mixmaster.

Scott