A Question About Hammered Coinage.

It comes down to what the monarch (or duke, or what have you) decides passes for current at a given time.

Some were known for keeping coinage stable (e.g., early florin); some for using the previous monarch's type (e.g., John not changing the penny's name from Henry); some for immediately and often recoining for seigniorage (e.g., Maximillian I); others for countermarking during revaluations (e.g., James VI in Scotland). It's pretty variable and at the whim (or needs) of the ruler.

A quick look at Spink shows E I & E II as hardly differentiable, whilst E III changed the fineness and weight some years into his reign -- I can only assume that would have been done with the intent of melting the better coinage to capture the difference as profit.

The older (more valuable) coins would still be good to an honest money changer (as their value back then was intrinsic), and larger purchases/exchanges based on weight and/or known fineness would require fewer older coins for a given quantity of newer (less valuable) coins. In simple coin-for-bread transactions, though, I don't see either party being the wiser.

This topic is surprisingly complex during the middle ages. It's much quicker to ask than answer :)