I have observed for 40 odd years and have 30 odd mainly Hi-quality binoculars in my collection I would count the Leitz’s in my top 5. These Leitz’s can be obtained at reasonable prices still and can be acquired for around ½ to the price of a new Pentax ED or similar - depending on condition. I do consider the Pentax ED's just below modern Alpha binoculars so really for 40 year old binocular the Leitz’s do hold up remarkably well which is tantamount to the original excellent optical and build qualities. Of course the Pentax’s are superior for eye relief and close focus - 17 mm / 6.5 ft. The early Leitz's are not waterproof but well-sealed against moisture. I found I had less lateral blackouts with the Leitzs. Ultimately the Pentax does have superior light transmission and more stars are seen however it is also 3 mm extra in aperture. Night time stars are equally pin point in both the binoculars. Whilst the Pentax does have a mildly brighter image with less CA, improved contrast and colour fidelity, the image in the Leitz is flatter and wider, 6.3 vs. They give my Pentax 10x43 ED’s a run for their money. There is mild pin cushioning but minimal other distortions or aberration’s. Since there reconditioning the image is again bright and sharp. Whilst the lack phase correction the image does remain remarkable considering their age. The optical and build qualities are still excellent on these early Leitz’s. My local Leica dealer in Auckland had originally quoted me $NZ1000 + / GBP480 + for the same treatment in Germany. Optrex, dissembled, de-stained the optics, cleaned, re-lubricated, reset, collimated and tested them and then replaced the perished rubber eye cups, all for the remarkable price of $NZ280/GBP135 pounds.
I have had the Lieitz’s for some 20 odd years. I sent them from New Zealand for servicing as they prisms were becoming increasingly tarnished and the image was dulling. I just received my 40 odd year old Leitz 10x40 BA Trinovid’s back from ‘Optrex’ in Surrey the UK.