RIH also had a 'model campagnolo' if I recall correctly.
So, here's where it gets fun, at least for me.
Any holes for headbadge? RIH used them, not sure about Presto.
Early Zielemans never did but towards the end of Ko's building he
did have a rather tacky headbadge. I have one, much prefer the
decals.
any serial number on the frame? engraving?
my latest Zieleman has very light KZ in seatstay caps one good
thick coat of paint and it would be nearly impossible to see.
Are there any distinguishing features around the lugs or are they
bog standard? maybe some detailed photos?

Marty