Mystery jelly

I've no idea what this is. I needed some plum jam for a recipe and had none, so was looking for the closest substitute. This unlabelled home-made stuff from last autumn looked the part so was used (and pronounced delicious by Mr B, but then he'll eat anything. It was for sticky baked lamb breast, as ribs, in case you want to know.) I think it may have been slightly-less-sweet-than-it-should-be Bramble Jelly.

Backblips for Saturday and Sunday.