I, too, fished the original Rapala, when I could finally afford it, back in the early 60's. Mine is snagged in the middle of an eastern Sierra Nevada trout stream.
Over the years I've bought many Rapala lures.
But their deep divers have/had fragile bills. They broke at the line tie if you hit them on a rock, or even slapped weeds off them on the water.
I figured it had to do with the metal in the bill, and maybe some weird painting process, like a radio-cured topcoat that caused stress at that point.
The DT series holds up much better, so they have obviously finally changed something.
I love their DT series.