sergio[Panerai Moderator]
5743
It will be a piece of cake for Anthony....
to answer your (may I add...easy...question) since he owns...both...of them 
Ciao
Well....
By: sergio : May 24th, 2015-08:17
the 21 is a 47mm Radiomir, the 22 is a Left-handed Luminor 44mm, the 23 is a Luminor 44mm GMT with "seconds" hand. So, in fact, not very similar to one another :-) Ciao