This part does not show up in our system. however if you can provide a partial or full schematic, we can try to help further. I have a gut feeling this is a general purpose diode. As I have a few similar 'GPxxx' diodes at home
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Grab the datasheet from this page/link and see page 8 - markings correlate. And I was able to further search our database to correlate to this family part, so that's a good thing