At the time, a guinea was a fairly large unit of currency. In poorer areas, like this village, they would appear relatively uncommonly as very little cost that much. Instead, they would see the smaller units - shillings, pence. That's what the first part of this phrase tells us... that in his village, they are rare.

When the coin does appear, it will likely be used to pay for something low-priced, which would result in large amounts of smaller coins in change.

Let's look at this information:

In the traditional pounds, shillings and pence system, there were 20 shillings per pound and 12 pence per shilling, and thus there were 240 pence in a pound.

Ignoring the fact that the value of the guinea wasn't always equivalent to the pound (though it was originally intended to be), let's use the exchange above. If you paid for something that cost 5 pence with your guinea, you'd get a lot of coins in change - 19 shillings and 7 pence.

So, instead of one coin, you'd end up with as many as twenty-six!

So, when they say "what a deal of money it brought in change" this is what they're talking about. "Change" is the money you get back when you pay more than you owe. "It" is the guinea.

At the time, a guinea was a fairly large unit of currency, made from gold. In poorer areas, like this village, they would appear relatively uncommonly as very little cost that much. Instead, they would see the smaller units - shillings, pence. That's what the first part of this phrase tells us... that in his village, they are rare.

When the coin does appear, it will likely be used to pay for something low-priced, which would result in large amounts of smaller coins in change.

Let's look at this information:

In the traditional pounds, shillings and pence system, there were 20 shillings per pound and 12 pence per shilling, and thus there were 240 pence in a pound.

Ignoring the fact that the value of the guinea wasn't always equivalent to the pound (though it was originally intended to be), let's use the exchange above. If you paid for something that cost 5 pence with your guinea, you'd get a lot of coins in change - 19 shillings and 7 pence.

So, instead of one coin, you'd end up with as many as twenty-six!

So, when they say "what a deal of money it brought in change" this is what they're talking about. "Change" is the money you get back when you pay more than you owe. "It" is the guinea.