has posted here
and the auction listing here
of a similar Baldwin & Jones Massey I with the patent mark beneath the cock. Jabez Baldwin ran a number of business in parallel, he is known to have been in partnership with John B Jones around 1815 in Boston.
More on the cap mark.
I thought I had seen it before on capped movements that found their way to America. Rich has two examples, Davis Brown & Co, Boston #507 & Samuel G Jones (no city but Philadelphia or Baltimore) #1210 the mark is either TF or JF in a gothic style.
The Jones example is interesting in that it is a Massey III with the lever mounted on a slide as is found with rack levers. This is by no means unique and other examples are known, both in the UK and on exported movements cased in America. Some may be conversions from racks, but it also believed that Massey escapements were fitted to rack frames and are therefore original. It is also know that early versions of Massey designs (I & II) were later converted to Massey IIis and I would not rule out that possibility with the Jones #1210.
I also have a suspicion that some (possibly the majority) of these Massey Is were made in Coventry - this ornament on the regulator scale
is frequently found on Vale & Co finished movements in the period when Edward Massey was in Coventry (the photograph is from an 1815 rack lever signed Vale & Comp). In my opinion a movement signed Robert Hill, Stafford #326, Massey I ~1815 with the lever mounted in a slide and carrying EMP 2690 on the underside of the cock foot, was probably finished by Vale & Co.
If I am correct and these movements were finished in Coventry, then we should be looking for a cap maker with the initials TF or JF working in Coventry. Vale and Rotherham movements from the late 1820s are known with caps stamped TF. This is thought to be the mark of Thomas Furneaux, a family of cap makers who were active for a considerable part of the C19th. I suspect this earlier mark is possibly an early mark of Thomas, or possibly that of an earlier relative.
While these are inferences on my part, I suspect they are not unrealistic.