Ithaca Flues Choke Markings

I have a 16 gauge Flues with 28 inch barrels, serial number 380XXX. It has nice wood, English stock, beaver tail forearm, and single trigger. I suspect it is a skeet gun as both barrels seem to choked the same and the safety is not automatic. Where would I find the choke markings? Each barrel has a number 4 marked on the bottom. Is this it or what does the 4 mean?

--jawinchester