While we were waiting for the bus home today, Olle explained to me and Oliver how QSL cards work: two ham radio operators establish a radio connection, the more distant and unlikely the better; during the connection they exchange call signs, which are globally-unique and can be used to look up a postal address; to mark the magical radio connection, a printed QSL card can thus be sent, acting as a kind of award of merit for defeating geography via radio.

Olle delivered this explanation in light of Ton’s proposal:

Letterpress printed QSL cards for successfully sent and received Webmentions must be the most finely targeted joke. The audience very likely not larger than 3 people.

Being interested in Webmentions, and also being a letterpress printer, I feel an obligation to make this happen.

Here, then, are the Indieweb building blocks:

• Olle writes a blog post.
• On my blog, I reference Olle’s blog post, and so my blog sends him a Webmention.
• Olle’s blog receives the Webmention, and looks to see if he’s ever received one from me before.
• He hasn’t!
• Olle’s blog looks for a postal address h-card on my blog and, finding one, sends a mailing label to Olle by email, ready for attaching to a letterpress-printed QSL card that he can pop in the mail to me.

For this to work as outlined:

1. Blog authors need to includ their postal mailing address on their blogs, marked up as an h-card. I’ve got this but not everyone does.
2. The Webmention-receiving logic on blogs needs to be able to track first contact, and trigger a QSL-card-sending callback when it’s established.
3. Letterpress QSL cards need to be printed. I can do this.

I agree with Ton that the audience is small. But we’ve already got 3 people, so the idea has already reached 100% of its estimated audience.