This the usual base mounting for tripods for quite a period of time. Some people make a round mahogany section which will fit in the hole with standard female 3/8 or 1/4" threads in the middle. Otherwise you can look for a set of 3 adjustable legs - without the platform -that will fit. Folmer made a lot of these and they are a commonly appearing item.
At this time, the ground glass was not "enhanced" by a fresnel.
Full plate size is a very useful size for contact prints. Availability can be a problem, but is always available from Ilford (at a price) through the once a year ordering process. This is just closed for 2016.
You can find info about the Albion - version 1 - on this page
http://piercevaubel.com/cam/scovill/albion.htm
There are a number of other versions on this splendid website.
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