Last text item

Question

this does not work.
I need to extract the name of the file dropped onto the droplet.
can anyone help.
on open the_files
repeat with a_file in the_files
tell application "Finder"
set AppleScript's text item delimiters to {":"}
-- display dialog a_file as string
--set the_file to a_file as string
get last text item of a_file as string
display dialog a_file as string
end tell
end repeat
end open

Answer 1

I got this to work so the result gives me the just file name (AR155Scott, Bobby Full mix.png), now I need to extract out just the AR155 part of the file name. any help would be appreciated. Thanks.
repeat with a_file in the_files
tell application "Finder"
set AppleScript's text item delimiters to {":"}
set the_file to a_file as string
set the_project to the last text item of the_file
display dialog the_project as string -- AR155 Scott, Bobby Full mix.png
--set the_project to last text item of a_file as string
-- display dialog the_project as string
end tell
end repeat