If you go to Wheatstone English Concertina price list for 1925 ( for instance), on the concertina.com website, it shows firstly the button layout for a 56 Treble... G to G four octaves from G below middle C. Then it will show the ranges of varius models.
But quickly and taking the 48 treble ( G below middle C to C above the fifth ledger line beyond the treble stave)... then the Tenor treble is a 56 that adds the notes down to C an octave below Middle C.
Tenor is usually a 48 that starts on the C an octave under middle C.
Baritone is either a 48 pitched a octave lower than a Treble or a 56 an octave belows the 56 Treble ( usually called an extended Treble).This has the Low G ( on the lowest line of the Bass clef) on the right hand end.Also exists in 64 key versions.
A Baritone-Treble is basically a treble with a keyboard that continues downwards keeping the same patern untill it reaches that G on the bottom line of the Bass clef , only now that note will be on the Left hand end. These come in 56, 62 and 64 key models.
There are variants and specials too. A wee bit confusing but this is the basics.
Basses exist in several sizes too, both single and double action.
Thanks Geoff - I really appreciate your help!