Here's a photo of an early Mills Operator Bell; looks like nothing unusual, but look more closely and you'll see "Mills" is embossed on the top casting inside the center oval below the reel strips.
This was posted on one of the Facebook groups by a long-time collector/restorer (he may be on this forum; T.E. are you here?) who said he'd never seen that before. He's probably more knowledgeable than me and I'm sure it's new to me too.
If anyone here has one in their collection like it, please let's see it.