Lockdales and the Komnenid Byzantine Coin

Here is an interesting auction on the internet host, www.the-saleroom.com:

Lot 1391 - Isaac I Comnenus, Byzantine two-thirds silver miliaresion, being sold by  Lockdales Coins and Collectables in their Auction #127

Isaac I Comnenus, 1st.September 1057 - 25th. December 1059, Byzantine two-thirds silver miliaresion, Constantinople Mint, weight 1.63g, diameter 23.03, obverse:- Christ's bust facing, with nimbus cruciger, wearing pallium and colobium, right hand raised giving benediction, book of Gospels in left hand, legend IC - XC, reverse:- Greek legend in six lines, KE RO[HO] / IC[AAKIW] / [OPOOAOIW] / [AECI IOT]H / [TW] KOMNH / NW, double lined border each side, Sear 1846, there is thought to be only three other specimens of this issue known, these all being in museums and from different dies to the present piece, the coin in the Dumbarton Oakes Collection was sold in 1948 and the only previous sale we can trace was in 1886. Present piece found with a metal detector on 1st. January 2015 in Mid-Suffolk, sold with all paperwork and research by Dr. Vezin, reverse has thin black deposit across legend, also very light scuffs, excessively rare and possibly the only specimen of this Byzantine Emperor in silver available to the private collector, VF/NF ...[more]

Interesting findspot, eh?  That "all paperwork" probably does not include a PAS report duplicating the database entry - because there seems to be none. Quite who "Dr Vezin" is, the auctioneer does not say.  It was probably Dr Roger Vezin, who wrote about other finds for Lockdales, but what significance that may have is unclear. What evidence is provided about the findspot?

Coins of the Komnenid emperors are not very common finds in the UK. Here's a map of the one in the PAS database (one from Bromley, near London - .SUR-8206C4)

[In general, the whole assemblage of later Byzantine coins in the PAS database look to me very much like modern losses - more  contamination of the UK archaeological record by manuport artefacts. Look at the state of preservation (corrosion). The coin of Michael II is noted as a modern loss. Here's a cast tourist fake - and a probable watch-chain fob piece . And what's this one about? Who is 'Mr Clough' and why is his military service reported in the PAS database?]

And here is where the coins of the Komnenid emperors were in circulation:

Here's where these coins circulated (left). Metal
detecting without a permit is forbidden in
this whole region today

There is a thick crust of black gunk not removed in the cleaning of this find. No analysis is referenced, but one very likely identification is silver sulphide. What "mid-Suffolk" soil conditions would lead to the formation of crusty silver sulphide? That is soil conditions in areas reached by metal detectors, in anaerobic soils with the soil water containing soluble sulfates and decaying organic matter, sulphate-reducing bacteria utilize available sulfates form hydrogen sulphides as a metabolic product. The hydrogen sulphide reacts with the silver to form silver sulphide [...]:

2Ag + H₂S >> Ag₂S + H₂

For this reason  silver sulphide (Ag2S) is the most common mineral alteration compound of silver from for example shipwrecks.

Where was this coin found? Who was the finder? Who is the landowner, and has Lockdales seen a finds release form signed by the landowner on whose land this (reportedly) was found? If not, why not? Does the seller have title to sell? What checks were carried out?