When the contribution system method came in in the early nineties, we were instructed NOT to ask, in the UK..[Charity rules we were told] If the H/H said "How much is it?" we said that they may contribute as they see fit...Very few people asked, though l recall a daft old lady who wanted to give us a £10 note - we refused because she did not seem to be fully "cognizant"...
In the old days we used to only leave lit. for the money . I recall the childhood mag presentation that always ended "two for ten pence"