I've a feeling this could be a genuine UK double-sided acetate cut by Decca in 1961. 78 acetates were still being cut right through the 60s and 70s, mainly because of the improved sound quality so that they could be played as backing tracks on TV programmes, mainly for the artist to mime to.
Judging by the sound quality of your acetate, it could be one of those that was rejected because of the poor quality.
Another theory thickens the plot. Acetates in the UK and US normally didn't have matrix numbers. I wonder if this was a test cut for a scheduled release somewhere else in the world? Probably the "11262" is the date on which the acetate was cut (ie, 11 February 1962).
As an aside, both tracks were pressed in India as 78s (Neil Sedaka on RCA and the Mar-Keys on London). Someone let an Indian 78 of "Last Night" go on Ebay for around £80 a few years ago. The Sedaka was also on 78 in South Africa, but not sure about the Mar-Keys.
With the possible date of February 1962 in mind, bear in mind how long records take to be released in another country - can be anything like 6 months after its original release. I've seen an Indian 78 of "Multiplication" by Bobby Darin. Whilst this was a UK Top 10 hit in 1961, the release year given on the Indian 78 is 1962 (a bit like the Billy Fury label scan in my next post below, which was also a 1961 UK hit - note the year of 'publication').
Hope this helps.