If I were to.....................

[mickvp]

On the label sewn usually to the strap of your helmet will be  a number something like 05XXXXX/P-0XXXXXX, or 05XXXXX/J-0XXXXXX  or finally 05XXXXX/P-J-0XXXXX
P is tested for full face approval
J is tested for open face approval
P-J is Full and open approval
Unless the helmet is approved P-J it is illegal to use a flip front helmet with the chin bar open.

I popped out and checked my Nolan N103 there (which I know has duel type approval) and it appears what you have said is sound :