I took a look on Vintage Machinery and found 2 Wells Index models that look similar.
I think that it may be made from parts of the lighter 756 model
http://vintagemachinery.org/pubs/2280/28639.pdf with a couple of risers .
They don't show risers on that link but may be shown in one of the other publications that I didn't check
This is the larger but similar looking model that lists as 500 lbs. heavier .
I didn't compare all the details.
Perhaps the base was shop made where ever it was being used.
I would guess that the machine was probably built as a portable drilling machine in place of a larger radial drill or magnetic base drill for use in some place like a ship yard ,railway shop or bridge work where it was easier to bring the machine to the part .
I have seen a horizontal drill brought by overhead crane to drill holes in the end of a large paper mill roll and depending on the job a small radial arm drill carried by the crane for another vertical drilling operation where the part weighed several times what the drill did.
I think the small milling table was probably added afterwards by someone who bought the machine when it was retired from its original purpose.
Jim