People get confused easily by old British coinage. I imported this list I made from the old realcent forum and I hope it helps.
The "d" they used to denote a penny is descended from denarius which was an ancient Latin/Roman currency term. The value expressed in "p" (pence) shown in the list is the theoretical conversion value in post-decimalization money on the current base 100 system.
Farthing ¼d (0.1p)
4 farthings = 1 penny
48 farthings = 1 shilling
960 farthings = £1
Half penny ½d (0.21p)
2 halfpennies = 1 penny
24 halfpennies = 1 shilling
480 halfpennies = £1
Slang: Ha'penny (hay penny)
Penny 1d (0.42p)
12 pennies = 1 shilling
240 pennies = £1
Three pence 3d (1.25p)
4 x three pence = 1 shilling
80 threepennies = £1
Slang: Thruppenny bit
Six pence 6d (2.5p)
2 x six pence = 1 shilling
40 sixpennies = £1
Slang: Tanner
Shilling 1/- (5p)
12 pence = 1 shilling
20 shillings = £1
Slang: Bob
Florin 2/- (10p)
24 pence = a florin
2 shillings = a florin
10 florins = £1
Half Crown 2/6 (12.5p)
30 pence = a half crown
2 s. 6d. = a half crown
8 half crowns = £1
Slang: Half dollar, Two n Six
Crown 5/- (25p)
60 pence = a Crown
5 Shillings = a crown
4 Crowns = £1
Bank Notes:
10 Shillings (10 Bob)
1 Pound (quid)
5 Pounds (fiver)
10 Pounds (tenner)
20 Pounds
50 Pounds
Progression:
2 farthing = 1 halfpenny, 2 halfpennies = 1 penny, 3 pennies = 1 thruppence, 2 thruppence = 1 Sixpence, 2 sixpence = 1 shilling, 2 shillings = 1 florin, 10 florins = 1 Pound (Gold Sovereign), 1 Pound & a shilling = one guinea.
Real World Price Expression pre-71:
Something that was 1 pound, 13 shillings, 11 pence, and 1 farthing would be expressed £1/13/11¼. Something that was 4 Shillings would be 4/-, and something 5 Shillings and 4 Pence would be 5/4 and something that was 3 pence would be 3d. A Guinea was 21 Shillings, or £1/1.