The date of publication is probably just a few pages in. Here are pictures of mine from '84 and '88 and they follow the same format. "Decimal Day" in the U.K. was February 15, 1971...that is when they changed the currency from the old, "pound, crown, shilling, pence" system to the current 100 pence to a pound, just like dollars and cents...so your rules are obviously older than that based on the price. By my research, it looks like that Rule Book costs about 1/10 of a pound so if it was somewhere near 1971, about a quarter or so.