I haven't looked throughthe high magnification custom shop models, but I do own a handful of old Japanese Tasco scopes and the glass is excellent throughout the entire magnification range. I have a 3-9x40, a 6-18x40 (Omni view), a 6-24x40 (target dot), and a 5-20x50 Mag model.
I recently replaced a Zeiss HD5 5-25x50 with the Japanese Tasco 5-20x50 on one of my rifles. The Zeiss HD glass was pretty good, but the old Tasco was sharper and brighter on like powers when compared side by side. So the Zeiss has a new owner and the Tasco now sits atop the rifle.
The 6-24 I own has a very clear and sharp image all the way to 24X. Great scope. The 6-18 is the same quality, but it has that wide field view which I absolutely love.
All 3 of my higher magnification Tasco models have medium height target turrets. The clicks are as solid as any high end scope on the market and they track very well. My 5-20x50 model even has a zero stop on the elevation turret and a total elevation travel of 44 MOA in a 1" tube. Tasco was way ahead of the game back in the 70s and 80s.
But the best thing of all...the most I paid for any one of those scopes was $135. And you could put them up against any mid priced Leupold VX3, Zeiss, Nikon, Vortex, etc and never be disappointed. Heck that Zeiss HD is an $1100 scope brand new and I felt that the old Tascos had better glass.
But as I said, I can't attest to the quality of the high magnification custom shop models, but I have been very pleased with all of my experiences using Japanese Tasco scopes. They can't be beat for the money if you can still find them. I pick them up when ever I find a deal on one just to have on hand. Now, don't get me wrong, they aren't the best scopes in the world, not like its Swarovski glass, but the quality to price ratio is so good they will never leave you feeling like you wasted your money.