I won an apparent Grubb B lens on eBay today - I was looking originally for a Grubb-C Aplanatic Pat. 1857 in order to share acquaintance with one of what Watkins apparently worked with. I looked up information in Vademecum and it seems that this meniscus style lens may have been labelled B even though they were usually labelled C previously? Were the other Bs RRs? What do I have here and from what year? My B lens has serial number 2890 and one sold a while back in another venue and labelled C has serial number 2795, same dimensions as mine (mine is 12" focal length). But, they look like the same lens design to me - see below (mine, labelled B is on the right). Can someone please elucidate? Thank you!