It's an LB, vintage 1930s or maybe 40s. To this day, Sunnen still differentiates between Industrial end users and Automotive end users; automotive machines were painted red. The oil cups reveal it's got Babbitt bearings, but the nature of honing with the expandable shoes means it really doesn't care whether the spindle has play, it will still make perfect holes. Current mandrels will fit, as will both concentric and eccentric bushings. We have a 1934 bench-top model just like yours only it didn't have a pump and tank, you had to spray oil on the work. Ours has been mounted on a shop-built tank with an electric pump and is used for only one job, using a $2000 custom-built mandrel--and it's just as good for the purpose as one of our newer Sunnens. The mandrel is the critical element, it doesn't much care what rotates it.