Bagley defiantly changed the density of the wood they used. The wood from the 60's was very light weight, in the 70s it got a little tougher and so on to today?s lures. Plus the paint that they use now is totally different than what they used to use. I personally like the old ones that the lips break out of if you whack them on the water or if a fish hits them they may take a chunk of wood. Although not as durable they are a much more reliable lure to me. And heck if I break them I can always fix them.
I had a guy send me a bunch of old BB's (probably 60s or 70s model) that were just totally destroyed. When he got them back he was amazed. I have to say that Bagley's are my specialty. Next time I rip one apart (should be soon) I will post picture for you all to see.
Believe it or not a lot of the BB4's that you guys have, have probably at one time or another was cut in half by Bagley. For what reason I do not know but a lot of them that I get to refinish have been cut right before the lure thins down for the tail and then glued back together. I don't know if maybe those are from a batch that were mis cut and made to small so they just cut them and added more length to them.
TM---- yes I do fish the ones with the lead in lip. Those old lips like I said may break easier but they make the lure run totally different than the new lips they use. Probably because the old lips are thinner and will vibrate. Heck I could be wrong on that thought.