Gentlemen,

Would the Marshall cross slide shown on the left fit the Moseley lathe (right)?

Only with a shoe to fit the Moseley bed. The Moseley bed locates accessories in the vee above the t-slot. The shoe on the slide rest appears to be for WW-pattern lathes which locate on flats on the outside edges of the bed. According to Perkins "Modern Watchmakers Lathe" the bed angles are 60 degrees for both styles. Hope this helps.
Regards,
Bob

I am imagining the shoe (lug, stop) fitting as follows (marked in yellow). Would this hold the cross slide properly?

Paul-
It should bear on both sides of the vee.
Regards,
Bob

for the most part Marshall cross slides fit all Moseley lathes as well as Peerless as both were made by Marshall. It will also fit any other American WW lathe.The cross slide usually fits on a support slide shoe that is attached by a through screw to the slot in the lathe,and then the slide is fully moveable and able to be positioned anywhere on the bed. Could you please show us a photo of the bottom of the slide? thank you,Tom

Here is the bottom view, Tom.

I'm pretty sure that it is not a resting foot,but a positioning bar to keep the slide at a certain position on the bed,the bar tapered on one side to rest against the side of the bed,the slide being positioned accordingly and locked in place on the foot with the long screw through the slot,a knurled large wheel below to tighten it up, and a lug above the foot to lock in the slide slot on top of the bed

Paul, Here are a couple pictures of what my Moseley cross slide looks like.

One more

Tom, if I get your drift, this slide WILL bolt onto the Moseley bed with some kind of screw. This Marshall slide is also shown and described in Perkins's lathe book (2003) on page 63: "There is an adjustable stop on the base that goes against the lathe bed to keep the slide rest aligned on the bed."

My question is, will the slide remain in place and the slide be operable? Can the bottom part of the slide rotate, or does it lock to 90 degrees with the bed? If anyone has used this arrangement, please come forward.

The Moseley slide in Robert McClelland's pictures obviously locks firmly to a 90 degree angle with the bed. I would certainly go for a Mosely slide if one were available, and this discussion would not be necessary. A great find, Robert.
.

yes when you use the screw plate foot it will lock where you put it. They are fairly easy to find. I saw one on eBay last week but it seems to be gone now.Yes it will rotate when on the foot, and lock at whatever angle you want. Rotation of the cutting plane is facilitated by turning the short plug on the one end that has a hole in it. You put in a steel rod and rotate a partial turn till it frees the rotary function,then re-lock it where you want it. Very simple to do my cross slide is shown with a screwdriver in the slot hole for freeing the rotary function and the slide is shown partially turned.