No it's not. The Slaney coin was bought by Geoff Cope and is vastly superior to this one. This is the ex Norweb coin which Roddy had for a while before selling it in one of the NY sales.
This is Bergne no.7 (NC 1855) which was described as:
No. 7.
Abraham Edmonds (bought by him casually),
Thomas Dimsdale. Bought at his sale in 1824, for 110, by
Thomas Thomas. do. 1844, for 48, by
The late James Dodsley Cuff.
(In a very good state ; but there is scratched on the field
of the obverse, C. W., Oct. 12, 1799.")
You can see traces of where the graffiti was subsequently polished out. However, in my view and that of others, it has also been plugged, which goes a long way to explaining how a dealer could pick it up so cheaply relative to other offerings around the end of the 18th century. If you look at II in the obverse legend, the facing uprights of the two characters are defective at the top giving a rounded profile to the vertical line. Compare that with the Slaney, Glenister or any other coin and these have perfectly formed Is.
The Slaney coin wasn't known to Bergne, so doesn't appear on his list.
CW may well be the initials of the jeweller or silversmith on the Strand that Edmonds acquired the coin from. Graffiti on a holed coin is not much more of an impediment to value, so this may be the coin that someone was touting around the 1740s but struggled to sell. Can't find the relevant document at the moment to give a name.
Discuss.