I was surprised by the number of people who had to google, I though people would generaly know a bit about the history of computing to be able to deduce the date. It's pretty clear that this is about a programmable computer rather than a spaghetti-board or any sort of difference engine, so it must be 1940s at the earliest. Noone would have presented a paper to the Royal Society on programming in 1942 - the UK and the US were both at war with Germany and Japan and computing was a sensitive (top-secret ultra-secure) technique, so all the suggested dates earlier than 1950 can be eliminated. The reference to "arithmetic checks included in every calculation" dates it as belonging to the era when all programs were about mathematical calculations (ballistics, code-breaking, and so on) so it antedates the first computer for business/office (as opposed to scientific/engineering) apps (marketing release in 1954, but in operational at JNLyons Ltd from end of 1951) so certainly not later than 1955. That eliminates all the offered dates except 1950.

I haven't a clue. I was astounded when I saw six.

Tom