I have used mostly second focal plane scopes. When I started out there were a lot of 3/4 inch and one-inch tubes and mostly fixed power scopes around. One of the first scopes I used had the cross hairs repaired and there was a square knot tied in the wire near the edge of the view. It had a 3/4-inch tube both windage dials had small brass clips that pressed done on the knobs and into notches to keep them from moving. I don't think it was gas filled either as it would fog up with weather changes. My how things have changed for the better in the field of shooting in just a few years. There wasn't such a thing as repeatability in scope adjustments they would be close but not anything like today's scopes. The glass quality and coatings are so far advanced today. the precision that they are ground to is hard to compare to yesteryears glass. The advancements in tube construction with different alloys, instead of steel making lighter and more resting to damage in tubes. The quality of the threads is way more advanced and so precise now that you have repeatability in the adjustments and precise adjustments. The coatings are far superior to those of the past as well, the seals and gas fill are like no other before them. Even a low-cost scope today I believe will outperform the highest quality scope of 60 to 70 years ago. It's kind of like comparing cars and trucks from that time to today, what do you mean you didn't have air conditioning and the heaters didn't keep your widows defrosted, you had to crank your own window down how absurd. Gotta admire today's things we are truly spoiled by our access to convinces, when you look around the world and see that most peoples are still walking or don't have a car, that they are still struggling to feed a family and don't have adequate medical, or teaching, contraception what's that.