The batches don't always end neatly on a thousand.

I only have one number recorded in 275xxx and, yes, it's a 1563, but these 1563s are what is sometimes called an "exotic" dial model and are sprinkled liberally about the serial ranges at this point. I have no problem with an 1163 MH also existing in the 275xxx range - it doesn't look like there were enough of these particular 1563s to use up a whole thousand anyway.