I have a 1974 Mirage ( XXX 449xx )with the pre-Type1 (Type 0 ?)choke in the lower bbl.
How early or late in the Type 0 run that may be I do not know. Several other Mirages here are choked too but they are all post-76 IIRC. But I'll check just fer grins.
1966? Early in the production they would make anything you want. Guns were built on order. Ithaca/Perazzi sold a few "non-catalogued" guns with tubes. 1976(75?) MT-6 and Comp V(TMS) generally considered the first year when they became common.
Donald, it's possible. I would have to see it in person. I've seen the pics. It could be a later rebarrel. The muzzle has a flare or bell mouth. Knurled top thread but the knurling is smaller diameter than MT6. I read somewhere that Daniele Perazzi felt it easier to obtain better patterns with non-tubed barrels. Easier to make also. This explains rarity. Then, as now, serious shooters were highly opinionated as to what was best. They would buy 2 or 3 barrel set with different chokes, length, weight. They purchased a Perazzi in the 60's or early 70's because they were serious. Then, as now, they bought the best.
It is possible the SBT guns had screw chokes a little earlier.. To fit a choketube to an O/U.. first had no sideribs.. Perazzi did not like the look of them.. and fitting the long taper to barrels that were flared to choketubes was even more expensive and time consuming.. Thus.. the MT-6 was the first O/U they built with choketubes in both barrels.. As CNC came into being..it became easier to get uniform barrel tapers and machine made sideribs that required very little fitting..Then the choketubes became popular..
Stan Baker use to put the Winchester choke in many TM-1's.. but that was aftermarket.. I still think the year for production was still very close to 1976.. Even the top full/choketube bottom came after that.. I don't recall ever seeing a barrel earlier.. Most of those were in the early 80's..
Today.. a screw choke is a cost saving thing..as it's simply a press of the button on a CNC..rather than having a barrelman hand tune a fixed choke..
Like I mentioned above the one I have is a '73. Just yesterday I acquired another bbl, a MX8, also a '73, with the same Type "0" tubes. If I have two example they just can't be all that rare. And the "new" bbl is a domestic market item (I presume) with no importer on it.
I'll get some comparison pix for you maybe tonite or sometime over the wkend.