Short answer: I believe you don't need one.
Long answer:
Content labels are governed by the FTC, here's a link to a page that shows what does & doesn't need a label:
http://www.ftc.gov/bcp/edu/pubs/business/textile/bus21.shtm#exceptIt's basically required on clothing and household textiles. I don't remember if it specifically mentions coinpurses, but handbags and luggage are exempt, as are cosmetic bags & totes. it might fall into one of those categories?
The catch is that if you choose to list the material content, then it has to be accurate even if disclosing it isn't required by law.
But I think you can list a % of recycled content without getting specific about the material if you want to use that in your marketing. i.e. "Contains 90% post-consumer recycled material."
I think. But I'm not entirely sure, to be honest.
oh- and if it's made of any % of wool, there are specific rules for that. :-)
congrats on your first sale!