Rod your stamp is from 1955, Hungary was not using roller or hammer for the CTO at that time, the CTO was printed in the corner of the stamps directly on the sheet, so 25 cto was printed on a 100 stamps sheets.. this is why the cancel is so clean
All true general practice leave place for exception, they probably have some kind of different CTO that was made time to time
But why your cancel don't have date in the midle is an interesting question
here a similar stamp with the printed CTO , I like those CTO, the cancel is so clean it don't hide to much the design
