It's still daylight, and thanks to Conor, here is the Letter Cassette version from Eire - posted same day delivery!
Very similar to the UK model, though the Irish cassette has just 15 minutes worth of tape to record a message on - and there's also a feedback card enclosed to return to An Post. According to Conor, the Irish Cassette Post began in November 1987, and about 2000 feedbacks had been received in early 1988. Not sure how much longer the service continued.
More examples please...
|Eire, Cassette Post Envelope|
|cassette tape (unused) & feedback card|