Differences from 645 to 745:
- blued slide on stainless frame
- single action only
- serrated black short-pull trigger
- smaller black sharp serrated hammer
- radically different rear sights, adj available only in last year of production
- wood stocks standard
- single side hammer block safety
- no decocker or option for one
- 745 has no firing pin lock..? Arrgh, I'll have to check this!
- thumb safety is large and elongated
- two adjustments for trigger: pre-travel and over travel
- much larger "competition style" button magazine release
- first year production "IPSC Anniversary" marked with reserved "DVC" serial number prefix
It's worth noting that the 2nd Gen .45's and also the 9mm compacts introduced (or foreshadowed?) the pressed-in non-removable barrel bushing that the full size single and double stack 2nd Gen 9mm pistols did not have. The 439, 539, 639, 459, 559 and 659 had the same removable barrel bushing as the 39/59.
I probably forgot some details... so 745 guys, help me out!