Here's my Plaston postbox/moneybox that I've had since I was 3 or 4 (1966/7).
Its plastic is still soft and squeezy despite being about 55 years old. The base has what looks like M89 just under where it says Plaston - would this be the mould number?
Alas it no longer has its stickers (I do remember scraping them off at about age 10. Bad Toad!) I've added a picture of what the collection time sticker looked like (good old internet!), but cant find any pics of the toy with its other stickers (I think there was a 1 for the collection).
The top would have had a 'Post office' sticker - I've found an image online of the type of postbox the toy is based on and include that as well.
Timmy Toad