> I have relatives who live in Donegal, Ireland. They don't even have house names, just their personal name and a townland.

Ha, yeah same with my relatives in Mayo. When sending wedding invites, my English (now) wife was so confused by it all. Particularly so when Mr/Mrs <FAMILY_NAME>, <TOWNLAND>, Mayo would be applicable to a lot of people so first names are a must :)

While it's imperfect, Eircode should help with this.

Having just purchased a house in rural Offaly where several houses have the exact same address (I guess the post person was supposed to know everyone's name?) Eircode is really helpful for disambiguation.

Bingo: Eircodes were invented for exactly this problem.

Eircodes are unique per delivery point, whereas 35% of addresses were (pre-Eircode) non-unique.

This caused problems for, e.g.:

(1) Delivery people, except the state postal provider (An Post). As you rightly said, An Post kept a note at the local post office (not centralised) of who lives where. For anyone else (e.g. FedEx) it would be literally impossible to tell where to deliver an item, if the address is non-unique.

(2) Ambulances not able to find the correct house.

(3) More complicated provisioning for, e.g., fibre broadband - how do you avoid incorrectly disconnecting a neighbour, if the neighbour has literally the same address as your customer?

Now, an Eircode is sufficient in itself to uniquely identify the delivery point.

To see this in action, go to Google Maps and put in an Eircode, e.g., "D02 AF30 Ireland".

Or go to https://www.eircode.ie/ and put in an Eircode, and the rest of the address will be shown.

But to go the other way (from address to Eircode) literally requires, for non-unique addresses, the person to click on the correct property on a map.

Of course, Google Maps has a problem in that it gives people the wrong eircode if I put in my mailing address (I currently live in a building with several apartments - haven't moved yet). Perhaps Google maps can't handle multiple postcodes per building?

Quite possibly, yes - or otherwise related to the non-unique mapping from address to Eircode.

The other way round should always work though, i.e., if you give Google Maps the Eircode then it should put the location marker in exactly the right place every time.

you're correct, but if people type my exact address "apt X, # streetname, <city>" it still gives them a very different eircode.

Given that more people are using google maps than finder.eircode.ie we might wind up with Google determining truth here.

The chaos is not caused by the changing drivers, but simply by the unclear adresses...