Although it varies by model ...in general, Brownign first introduced the Invecotor chokes in 1983 / and barrels started being backbored and they went to the Invecotor Plus chokes in 1990.
Browning - for the last 2 years has not offered any of the Citori or the Cynergy line of Over Unders in a 16ga ( in either the 2011 or 2012 catalog ) .....although Browning does make a lot of guns that are not in their standard catalog for bigger dealers if they order at least 50 of that model in the spec they want ( like a 28ga in the Citori XS Skeet line / where it is only offered in a 12ga or 20ga ) ....there are quite a few of this model around, still new in box, in the 28ga made on the 20ga receiver for a big dealer in my area ( in fact I have one in 28ga and in a .410 ) that I bought new in box a few yrs ago ....
The only 16ga shotguns I see in the current catalog ...are showing up in their pump guns ...like the BPS Hunter model.
...so all of that just adds to why I think a 16ga is a bad investment / unless you want to keep it youself longterm.
16ga shells in my area ...are $4- $8 per box more than 12ga or 20ga ( making them $ 10 - $ 14 a box ).....so if you're going to shoot the 16 ga much at all ...reloading is probably smart as well...but getting hulls to reload is going to be an issue as well.
If you want to buy a shotgun as an investment ---a 12ga is a way smarter choice / although I'd recommend you buy what you want to shoot - and not worry about the investment idea. Browning Citori's do appreciate - or at least they have in the last 25 yrs....but what's really driving the used prices up - is the durabiltiy of the Citori line ( and the fact that they are today making about 39 different models of the Citori ) ...and prices are up quite a bit ...with price increases coming most every year as long as I can remember. As shotguns get more specialized .....these days ....with some models of the Citori designed more as "sporting clays guns", "Skeet guns", "Trap Guns" ....and Field guns....buying the entry level Citori's - like the Lightning or White Lightning...are even a little more risky in terms of investments. While all of the guns in the Citori line are solid guns.../ they share the same legendary barrel to receiver connection....not all of the models will fit all shooters...and the different models are very different.
Here is the list of available Citori's from Browning website...