Here’s one from me for you to try. And I’ve even given you all the possible views.
Hopefully I am not too late to play.
I'd guess ~28J
It looks like a Curvy Kate bra and I think the go up to a K cup?
It’s a 32K Curvy Kate Portia. I’d say it’s a reasonably good fit on the woman modelling it. The centre gore is snug, the boobs are encased in the cups with no overspill or side boob (although you’ll notice her boobs are being slightly pulled west-east - you can tell by where her nipples are positioned in the cups, but this is more to do with how her boobs are “set” - which varies from person to person), the straps don’t seem to be straining, and the back band is nice and horizontal/low. Overall - it looks snug and reasonably comfortable (although might be a tiny bit tight - which will be due to her cup size).
It’s difficult to give a proper size assessment without knowing more about her weight/height, but you can usually get close by judging the projection/volume of her boobs - even if I didn’t already know her size, I’d be thinking she was a relatively low back band (28-32, but most likely 30-32) and a big cup size (J-K/KK). So, if she came to see me and was wearing this bra, I’d be making a guess in the 30-32 range and J-K cup.
But it’s not an exact science.