5d coins were only issued by London, Canterbury and Bury, and have a new style of portrait compared to earlier issues. The coarse bust type, 5d1, is known for Canterbury only. 5d2 coins are relatively common for Canterbury, but rare for London. 5d3 coins exist for all three mints, but again are commonest for Canterbury. 5d1 coins have been considered by some as continental imitations.
...All have X5, R3 lettering:
We need to look mainly at the bust style to differentiate between the 5d sub-classes, and also at the crown end ornaments to help distinguish between 5d2 and 5d3.
5d1: X5 R3 - Crude bust, with half fleur crown ends
5d2: X5 R3 - More realistic bust, as per later coins e.g as for 5g, but with half fleur crown ends
5d3: X5 R3 - Neater bust, finer than other voided long cross pennies. Distinctive sharp crown ends rather than half fleurs. Distinctive central fleur. Often has a split crownband.
Some examples of Class 5d coins:
5d1 5d2 5d3