Philips "Implotec" SOD-87 Diode Markings?

[Chris56000]

Hi!

I have a PCB to repair with a very large number of the glass SOD-87 (MELF) diodes (black appearance, NOT red or colour-band marked) with white numbers round them to denote the cathode, these are marked:-

"1" with a forward drop of about 0.6V;

"7" with a forward drop of about 0.48V;

"9" with a forward drop of about 0.17V

I know they're Philip's "Implotec" package as all the data-sheets show a load of "X" markings in the same places, but not one of the datasheets for the types I can find actually says what the marked number means!

Anybody familiar with these who can offer a clue?

Chris Williams