Tourists and Rome residents have been joining lengthy queues to obtain the Vatican’s "Sede vacante" postage stamps, which went on sale on Friday 1 March following the retirement of Pope Benedict XVI the previous evening. The stamps, which are seen as highly collectable, are only issued during the interregnum, the period when the Holy See is vacant before the election of a new pope.

They come in a series of four and each stamp has a different value: €0.70 (letters and cards for postage in Italy) with a light green background; €0.85 (for Europe) with a pale blue background; €2 (Asia, Africa and the Americas) with a grey background; and €2.50 (Oceania) with a light yellow background.

The stamps are not for individual sale and must be bought in a series. The presentation folder featuring all four stamps costs €15, while a smaller folder with two stamps, created on Benedict XVI's renunciation of the pontificate, costs €10. The series of stamps can also be bought "loose" for their actual value.

The initial print run was for 230,000 complete series of the stamps whose use for postage is permitted only until the new pope is elected. However the Vatican post offices in St Peter’s Square – open Mon-Sat from 08.30-18.30 – will continue to sell them to collectors after the election of the new pope, for philatelic use.

Designed by Italian artist Daniela Longo, the stamps depict an angel with two keys surmounted by an ombrellino (canopy), the heraldic arms of the Vatican chamberlain or camerlengo. The chamberlain acts as the administrator of the Holy See during the Sede vacante, with the role being performed by the Vatican secretary of state, Cardinal Tarcisio Bertone.

This is the seventh series of Sede vacante stamps to be issued since the Vatican City was established as an independent state in 1929; the first series was released in February 1939 following the death of Pope Pius XI.

Meanwhile in May a €2 Sede vacante coin will be issued. Due to EU rules, the Vatican is only allowed to circulate one coin per year, with an extra one permitted in the case of a Sede Vacante. There will be 125,000 Sede vacante coins released – featuring the camerlengo logo – while in April another coin featuring an image of Benedict XVI will be released.

However an additional 10,000 silver €5 coins and 5,000 gold €10 Sede vacante coins are also due to be minted, for collector's use only.