Note that the four digit channel number beginning with the digits "10" indicates simplex use of the ship station transmit side of what had been an international duplex channel.  These new channel numbers, now recognized internationally, were previously designated in the US by the two digit channel number ending with the letter "A".  That is, the international channel 1005 has been designated in the US by channel 05A, and the US Coast Guard channel 1022 has been designated in the US as channel 22A.  Four digit channels beginning with "20", sometimes shown by the two-digit channel number ending with the letter "B", indicates simplex use of the coast station transmit side of what normally was an international duplex channel. The U.S. does not currently use "B" or "20NN" channels in the VHF maritime band. Some VHF transceivers are equipped with an "International - U.S." switch to avoid conflicting use of these channels.  See ITU Radio Regulation Appendix 18 and ITU-R M.1084-5 Annex 4, summarized here.

These new channel numbers should eventually begin to be displayed on new models of VHF marine radios.