Many Hoya's have very similar looking leaves as well as blooms. The letters and numbers like (NN031701) on a label are denoted by the nursery where the plant originated. For instance, the late David Liddle's Hoya Nursery in Australia cataloged all of their Hoya plants with the letters IML and a numerical number.
IML are the initials of his wife Iris Marie Liddle.

A few cuttings I received from the David Liddle Nursery about 12 years ago were labeled:
IML0079 Hoya acuta
IML0152 Hoya magnifica
IML0734 Hoya citrina
IML 0107 Hoya memoria, etc.
Cora, I searched and searched and couldn't find a Hoya with the cultivar name of 'Nona', could the spelling possibly be 'Noona'?
I found a couple of references to Hoya 'Noona' with the NN 031701 notation, a Thailand website for AH Hoya Nursery and a Facebook Page for Garden Paradise, Singapore. There are also numerous pinterest photos of a cultivar named 'Noona'.