Numbering unit SM52

[mantman]

Hello I am facing issue of numbers will not print on paper even though I put max pressure of numbering unit.
I am using numbering boxes of GTO -I presume they are the same for SM-. One thing i noticed that after manually throw on impression of numbering and sliding a paper between box/jacket, after folding it several times -close to -0,5 mm- it snagged the piece.
Could it be the jackets are wrong? Not sure if jackets are original from Heidelberg or aftermarket.

 

[boooch]

The numbering heads on the SM52 and GTO52 are different, as are the cylinder diameters.

 

[mantman]

The numbering heads on the SM52 and GTO52 are different, as are the cylinder diameters.

Thank you for your reply, heads as in boxes? I am not so sure i looked it up at sites selling numbering boxes and they say GTO/SM.