One possible cause of confusion in terms of a hash (#) being called pound (£) in the US was that (as I recall even in the mid-1980s) in many cases with ASCII/EB

One possible cause of confusion in terms of a hash (#) being called pound (£) in the US was that (as I recall even in the mid-1980s) in many cases with ASCII/EBCDIC character set terminals and printers the same number code displayed as a # in the US but as a £ (pound) in the UK (eg ISO646 vs BS4730, or EBCDIC 297 vs 37). So when cross-Atlantic conversations occurred the US would hear/read us in the UK refer to (they thought) # by the name pound, when we thought we were describing the actual pound (£) character that we were seeing on our end.