I have a few 1940-50s vintage Butler bins with ground level doors and you can't keep the mice out of them. I have two early 60s vintage Butlers with full height ground level doors that are actually mouse-proof. Doors fit so tight that they actually keep mice out! My newer bins have the doors raised about a band, plus they fit tightly so they're mouse proof too.

I second your comment about the Brandt vac for the old bins. Especially for my two that have had aeration pipes set on the floor. Trying to empty with a sweep auger took some scoop shovel work.