Update on those blades from Germany, those blades I've never seen before turned out to be crown tooth blades! I found a picture and reference about them in a old book from 2002 The n we scroll saw handbook. They class them as two way cutting blades, I've had a quick test run and you have to slow the feed rate down quite a lot, but not much tear out but the kerf seems to be a little more than normal reverse cutting blades no7 used in my text ,all the blades come with rounded backs, haven't had time to have a play with some of the other types.