Whenever I have bought a ticket at the ticket office I tell the clerk my age and get the discount, I have never been asked for proof of age - how sad is that !
It saves my Employer money, not me personnally as I claim my train fares back from work. I don't think the accounts dept even notice the saving. Maybe I could get an age discount on Paris Taxis, they seem horribly expensive. The last one was c.Euro65 from CDG to Montparnasse !!!!!