On February 17, 2013, Casascius released these coins saying “This is being added due to the rise in bitcoin value”. The price of Bitcoin had risen from under 14 USD to nearly 30 USD within a couple of weeks.
As with the 2013 series 2 1 BTC coins, there is a ‘lobe’ on the private key and its pit to ensure correct positioning.
It is known that at least 42 0.5 BTC coins were late-funded in 2015 and 2016. It is unknown how many of them are of this variety.