when was the switch?

[triggerman42]

What year did Browning switch from the invector to the invector plus chokes?
I just picked up a Citori with the NM date code , so made in 1990. It has the regular short invector system.
Before I looked up the code year , I assumed it was an earlier made gun. I figured mid 80's.
When was the switch?

 

[rembolt]

I beleive the invector plus choke was introduced around 1991 from what I can find the Citori plus O/U was the first gun with invector plus . Other models changed after that .

 

[scott9001]

i am under assumption that they changed to the plus in 92 correct me if i am wrong?

 

[3macs1]

As stated it started in early 91 with the BT 99 and just spread from there to the other models
Cheers