U.S. and Worldwide Stamps and Covers

1850 600r black, used in combination with two perf. 20r Dom Pedro (on back), on registered cover (opened for display) from Rio de Janeiro to Napoli, stamps tied by mute cancels, with unclear departure pmk alongside, docketing indicates 20 Feb 1870, red "PD" and "Registrada" in oval, arrival markings on back, some toning, otherwise fine, signed Roger Calves, with 1991 Diena certificate, also 2015 Brian Moorhouse certificate ("the basic letter rate in 1870 from Brazil to Napoli was 430r, with additional 430r for registered overseas mail, or total 860r. This cover is therefore underpaid by 220r. A possible explanation for the franking on this cover, might be that the registration fee was mistakenly charged at the domestic rate of 200r, in which case the cover would have been overfranked by 10r")
Estimate: $750