I think the first custom shops came in in 1994. The early ones were all 8-40 mag and had 1/8th clicks. They also had some unusual rets. I had one of these early ones for years (until last year in fact, owned it since 94/95) and it was a great rangefinder. This one didn't even say Custom Shop on the occular bell, just Tasco.
After a few years the 10-50 and 12-60 power versions came out, by this time the turrets were 1/4 MOA and mill-dot rets were available. Optics seem a bit more hit or miss on these later ones. All the 1/8 MOA turret 8-40 power versions I've had have at least been okay. The 10-50 and 12-60 have longer bodies between the turret and front bell.
My MK1 Custom Shop(s) came down to about 10 yards.
My main scope is one of the first DMPs. 10-50 power with no IR, very much like a Custom Shop but with the big turrets. This scope is 1999 or 2000 vintage. Later DMPs (also branded Nite Tec) had IR and a gear driven zoom ring that turns the other direction. These scopes focus down to 8 yards.
Don't know about the Big Nikko, but I think the Big BSA came in around 98/99, Nikko followed a few years later?