Crosman 766 questions

[happymecanic]

Hi all, I have this 766 to clean up and re-seal (I already have the seal kit), and I came upon a few oddities I'd like to know more about, if possible.

If I ''read'' the serial number right, which is 127701555, this rifle was made in december of 1977, which would make it a first variant, right? OK, so now this rifle has the steel tapered barrel shroud, which belongs to the second variant, but it also has the integrated receiver/valve assembly (for lack of a better term), which was used on the first variant only. Could it be a ''transitionnal'' model between the first and second variants? I know this rifle belonged to a Canadian Crosman sales rep (only owner), maybe he was sent an early example of the second var to show up  .

The pump arm ''lock'', usually a plastic ring thingy, is also different. It's a plastic plunger with a conical spring and a plastic base (see picture). Never saw anything like that on the first or second variant EVPs  .

Also there's a ''pocket'' atop of the receiver, just over the BB loading port. It seem to have served a purpose somewhere in the past (there's light wear marks), but what purpose? On the first and second variant EVP, you see two parts, 766A020 and 766-019, what are they? They look like a spring and a plunger, but not sure  . (Edit: could it be the bolt lock?)

Any help/hints appreciated 

[Tack Driver 10]

I have a few of these V1s.

What you have is a 766 V1 made after 1977.
It has the tapered steel barrel shroud and plunger style arm lock as shown in the Crosman IPB.
The pocket in the breech is for a spring and pin to regulate the BB feed.
I take all the BB related parts out as I don't shoot BBs and it makes the gun much easier to reassemble.

You can convert your 766 into a V2 which is a much better gun.
I usually take the integrated breech and machine it into a 1 piece breech in .177 or 22 cal.

Here's a link to the 766 IPB:
https://support.crosman.com/hc/en-us/search?utf8=%E2%9C%93&category=200223634&query=766&commit=Search