Green’s Dictionary of Slang

Blackford-block n.

also Blackford swell, ...toff
[the London clothes-hire firm of Blackford’s + SE block, the wooden head on which wigs were displayed/swell n.1 (1)/toff n. (4)]

a sporadically well-dressed man.

Show quotations
‘The Boy about Town’ [music hall song] He looks very well that’s beyond all dispute / For at Blackford’s he’s rigged up and down, / For Blackford lends suits, from the hat to the boots, / And that just suits the Boy about Town [F&H].