If anyone is still interested in a 1937 2+B proof penny, this part set I have listed on ebay contains one: https://www.ebay.co.uk/itm/285129613598
It isn't B.Unc, sadly, having had some handling, contact marks and I suspect circulation, but I am sure it is an impaired proof as it still has enough of the mirror finish when angled into the light. It was in my collection until I managed to get hold of a better one! So, I thought I'd throw it in with the part set...