My views on this are well known, but given the opportunity - I will bore you with them here once more!
Quality was always there. Look at locks made in the 1860s and 1870s - they are better than anything made since when at their best. Truly hand made and absolutely beautiful.
The 1930s was a period in which most of the mechanisms we now regard as essential and modern were well perfected. Also, materials were available in good quality and there were still plenty of time-served gunmakers at the top of their trade.
However, 1930s QUALITY is no better than quality from any other era.
1930s MECHANICAL PERFECTION, married to QUALITY may well be better, and a lot of 1930s best guns remained little used, as a bit of a scrap in Europe and elsewhere interrupted seasons 1939-45 and after that a lot of people were not able to afford the scale of shooting that they once were. A lot of mint guns got put away. So, today we see quite a lot of very nice condition, good quality, mechanically modern best English guns.
Victorian guns often got shot to bits, as did Edwardian ones. Lots of big-bag days, lots of years shooting before WW1 and lots of corrosive primers.
Best guns from 1900 to 1930 are every bit as good as anything buildt from 1930-1939. Just avoid iffy single triggers and ejector systems and guns that have been worn out.
John is right about lightweight - a thirties trend. To the current fashion, it is a bit of an annoyance - shorter barrels, lighter guns etc. If you want a long barrelled Purdey sidelock, you will find the pre WW1 era more likely as a hunting ground than the '30s.
