Hot air mail

Eric included this mysterious postcard in his envelope from the 2014 exchange.

The 8 in a circle looks familiar for some reason, but I couldn't figure it out.

I even scanned the image and ran it through a couple of web searches - no luck. I downloaded a scanning app on my phone - the bar code just says the same code on the card - 4HNC. 4HNC is a code for a protein, not sure if that is a clue or a red herring. Does the PL in IPL-33 etc refer to me?

In the end I decided to not worry about it, and sent Eric some hot air right back.

I had a bash at decorating the address side, although I don't think the small balloon will lift the large basket off the ground.

Update: Eric has resolved the mystery - see his blog post here.