Mystery Harvest

I have checked on these mystery fruit every now and then, waiting for some sign that will identify them. In all that time they have not changed - same size, same colour - today I tried picking one, and it came off easily, as did three more, so I assume they're ripe. There is still one left (I discovered three after that blip).

I have just eaten one; it's quite pleasant, I think a greengage. If it isn't, this may be my last blip!