I'll agree with that..... the box looks to be more 1960s to me. It's quite sturdy - they got a little thinner in the cardboard during the 70s.
Sometimes in these cases, a price will give it away.
In those days, the manufacturer being able to fix the retail price was perfectly legal - unlike today, and set prices remained that way for a long time. The notion of inflation set in during the 1970s and prices went up fast.
Sometimes the retailer would pencil the catalogue-sale-price on the box, often the lid or label-end and this would tell you the age from the manufacturer's catalogue price.
If the price was in pounds/shillings/pence (or in shillings and pence) then, broadly speaking, it was pe-1970; if it were priced in decimal only, post 1971. There was a period of a year or two either side of the change-over in 1971 when you may see both, but not often.
Some retailers at the time took the opportunity to 'round-up' or to 'adjust' the prices to the newer decimal rate with a little built-in inflation.....
As for the plane, I think that it was at the entry-level-end from a well-known maker, being polite about it. However, it may well be a good user with some sympathetic 'fettling'.
The fact that it has the box in reasonable condition, nowadays that's a value-bonus for certain collectors.
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