There are at least three vendors out there: Apex (whom the PACSCL
institutions used), Pacific Data, and ArchProteus. Each has very different
approaches to marking up, each does a decent job, but all will return files
that will require some degree of reworking.
One of the more significant differences for legacy finding aids is that Apex
prefers to work with paper finding aids, which they rekey (using triple
keying at a high rate of accuracy), whereas ArchProteus and PacData charge
at a lower rate if you provide finding aids as electronic files. So... if
you have paper and only paper, Apex may be more cost effective. RLG
institutions get a "lower" rate at Apex (it actually means that everyone
else is charged more, rather than RLG is charged less), but there are quite
a number of factors that can enter into cost.
I have addresses/contacts that I can supply off list, if you wish. They've
just had plenty of advertising as is.
American Philosophical Society
105 South Fifth Street
Philadelphia, PA 19106-3386