Ithaca Flues.....
 

....chokes. The barrel flats on this particular 12 gauge show a '4' on the left and a '0' on the right. Does this indicate full for the '4' and cylinder for the '0'? Thank you!

Yep. I have the same combo on my flues 12.

Thank you!

That's how my 1911 16 Gauge Flues is choked and I like it. Perfect for birds.

Were all Ithaca Flues chokes marked on the barrel flats?

Its my understanding that they were, but I may stand corrected.

I have some that are not stamped on the flats and others that are.

Fred, Could you post the approx. serial number range of those that are, and are not marked. Also, do you know if the gauge of the gun plays any part in whether or not the choke numbers are marked?

Austin,
I don't believe the stamping had to do with gauge. I believe it was different time periods of manufacture.
I have only 20 and 28 gauge guns so I can't speak to the other gauges. Some of my guns have no choke stamping, others have just one digit 1-4, and then some are in fractions, 0/4,- 4/4.
These are the only pictures that I have with me.
I am finishing the last weekend of turkey season, but will post photos when i return home.

In my younger and more formative years I paid a gunsmith 50 bucks to tell me what was stamped on the bottom of my barrels, learned my lesson and bought a stan baker bore gauge. Anyways I looked at all my flues and came up with the following
20 ga twist barrels SN183298 not marked
16 ga chine Damascus SN303172 marked 2 and 4
12 ga smokeless powder steel SN343020 marked 0 and 4