How do I get this widget made (a small rectangular bit of 1.6mm mild steel)

[Jonathan]

Grinding would involve somebody with a surface grinder and small vice.

Surely a magnetic 'vice' would be easiest, or is it just too small?

[m_c]

Magnetic chucks are only any good for items with large flat surfaces, not holding a small flat bit on edge.

A small vice mounted on the magnetic chuck, with the metal spaced appropriately would work fine.

[Jonathan]

Magnetic chucks are only any good for items with large flat surfaces, not holding a small flat bit on edge.

I was just thinking of using the magnetic chuck to hold it whilst grinding the larger faces, but fair enough if it's no use for either...

[m_c]

It would be fine for that, but not for doing the edges which is what the OP is looking for.

One option would be cut them from slightly thicker metal, then grind them to thickness.

[Swarfing]

Or stack multiples on edge together and grind the lot?

[HankMcSpank]

I am wondering here if my lowly cnc machine could be pressed into service to get a reasonable finish on on the top visible edge ....drop a part into a pre cut slot on a holding jig....tighten a couple of holding screws, then run a dremel (fitted with a grinding wheel) along the top edge to a very fine depth? (the depth being so minute, that I doubt my machine would get stressed?)

[m_c]

Try it and see?
Not going to cost you much, and might produce a good enough finish for what you want.

Another option I just thought of, is cut to near size then finish on a linisher (aka belt sander) using a jig to set depth. You're not really needing the accuracy of grinding, and a linisher can produce as good a finish, but just not as accurately, but they are capable of removing metal far quicker than a surface grinder.
And thinking along similar lines, maybe a worden style of grinder?