Just a very poor attempt at a forgery I think. Like has been said, it should not have got into the catalogue if anybody bothered to examine it properly.
Nice list Yaseen.
Just a few more varieties that i know of as follows:-
1817 Unbarred H In Honi
1817 RFX for REX
1819 9/3 (in the royal mint)
1819 9/6
1819 9/9
1820 20/20