Dear John,
We deal with US (and other) shares all the time, and I agree with the other comments so far, but if the Liberty Latin America shares are worth less than US$10,000 Computershare will usually waive the Medallion requirement. Liberty Latin America is a nightmare because of the small number of shares involved - it is a typical american rip off on honest long term shareholders of the former company just to wipe them out.
As for escheatment, this will usually be to Delaware. They also are just incompetent and lose documents and then take 90 days to reply to anything. We have been forced to say to clients we will help you make the claim (it can be done online), but chasing is for the client. We have not had clients receive any cheque from Delaware for years. Even complaints just get ignored.
You have to file all the usual documents with Computershare USA (not UK - which deals with Liberty Global and will sell the Liberty Global shares for you - cheaper than using the usual brokers) - Aff of Domicile; Form W-8BEN and W-8BEN-E; as well as a sealed and certified copy of the Grant (not a sealed copy, but certified by the Probate Registry (Form PA1S is the form to use for such purpose). This takes months in these covid times, so make sure this is the last document to be obtained prior to sending everything off to Computershare for processing as then you will be within the 60 days.
As for the Medallions, Fraser & Fraser also offer Medallions (contact their Sally Morgan).
Be aware that any cheque from Computershare USA will be in the name of the deceased and so you will have another nightmare banking the same. Computershare USA will NOT issue cheques to law firms or the Executors so you have the deal with the local UK banks to cash the same.
Yours sincerely,
Peter Double / Probate Resealing Services