Those commonwealth issues look funny to British-oriented eyes, but they were perfectly normal to the locals, as they were a Robinson Crusoe-ish compromise between the official currency (sterling) and the denominations the locals actually used:
Third-farthing (Malta): actually one grani, as on 9th June 1825, the governor proclaimed that the crown would be received for 3 scudi. As each scudo was 240 grani it follows that the penny was equal to 12 grani.
One thirteenth of a shilling (Jersey): actually 2 sous, as in 1841, the British pound was fixed at 26 livres of 20 sous each. A shilling was therefore 26 sous. I suspect that in 1813, the 18 pence and the 3 shillings went for 2 livres and 4 livres.
values of 1/4 and 1/2 of a larger denomination, such as the 2-1/2 gulden and the half crown are far descendants of the long-standing Spanish system of a peso of 8 reales, each worth 32 maravedis, with silver coins of 8, 4, 2, 1 and sometimes 1/2 real(es). As the crown and the leeuwendaalder were competing with the peso, the halfcrown was competing with the 4 reales coin. Likewise, the farthings, halfpennies, three-farthings and pennies were inspired by small Spanish silver. The Portuegese 2-1/2 escudo can also be explained by the erstwhile Spanish system.
That leaves the noble and angel, but you could also have mentioned the Dutch gold rider, going for 7 gulden. These rates are quotes of convenience. In reality, gold and silver coins were separate monetary systems. There was of course a conversion rate between gold and silver coin, but it was a market rate, depending also on the gold and silver content of coins. Saying that 7 gulden is a funny denomination is akin to saying that a dollar is a funny denomination, because it is 70 eurocents, while a pound is not a funny denomination, because it is 100 eurocents.
Peter