Promo codes for OsmTrails app, or in-app Map purchase. If you don't use a promo code and buy it, there is a 48-hour refund policy (and refund button) from the Play Store.
New Promo codes for OsmTrails app and OsmTrails-Lite app, or in-app Map purchase.
The Google Play console does not give me a list of which codes are used. Test them all. Email me if they are all used.