There's been a number of fake (claimed to be original) ARP plaques and door signs on the market for a number of years. The more common ones are the circular and rectangular ARP Warden plaques surmounted by a crown. They are very light compared to the originals. The below fake has been posted on eBay several times. The giveaway here is that someone didn't do their research. There is no such thing as an "Air Raid Warden Post"... there's an "Air Raid Wardens' Post". There was always more than one person at a post. Also, back in the day, grammar and punctuation was much more stringently followed. If you find a sign with the missing apostrophe chances are it's a fake/reproduction. Stating something is a repro is fine, but calling the below 'original' is simply lying.
News about interesting insignia, ARP related info and period photos that turn up.