Hi, to answer your question it is a 25p coin but you can't spend it as it has no value written on it. I used to take them to the bank until 6 months a go. As for selling price, I sell them for £2 In original case and loose £1 or 3 for £2. This also goes for 1965, 1972, 1977 and 1980 crown. Hope this helps.
The crown is the same size as the £5 coin, they changed it as was no longer profitable to make and sell these as 25p crowns.