Microstates : 10 a Sovereign Military Order of Malta (SMOM)

The Sovereign Military Hospitaller Order of Saint John of Jerusalem of Rhodes and of Malta (Italian: Sovrano Militare Ordine Ospedaliero di San Giovanni di Gerusalemme di Rodi e di Malta), also known as the Sovereign Military Order of Malta (SMOM), is a Roman Catholic lay religious order, traditionally of military, chivalrous, noble nature. It is the world's oldest surviving order of chivalry. The Sovereign Military Order of Malta is headquartered in Rome, Italy, and is widely considered a sovereign subject of international law.
SMOM is the modern continuation of the original medieval order of Saint John of Jerusalem, known as the Knights Hospitaller, a group founded in Jerusalem about 1050 as an Amalfitan hospital to provide care for poor and sick pilgrims to the Holy Land. After the conquest of Jerusalem in 1099 during the First Crusade, it became a military order under its own charter. Following the loss of Christian held territories of the Holy Land to Muslims, the Order operated from Rhodes (1310–1523), and later from Malta (1530–1798), over which it was sovereign.
Although this state came to an end with the ejection of the Order from Malta by Napoleon, the Order as such survived. It retains its claims of sovereignty under international law and has been granted permanent observer status at the United Nations.

Fra Matthew Festing - 79th grand master of the SMOM

However, unlike the Holy See, which is sovereign over Vatican City, SMOM has had no sovereign territory (other than Fort St Angelo in Malta and a few properties in Italy with extraterritoriality) since the loss of the island of Malta in 1798. The United Nations does not classify it as a "non-member state" but as one of the "entities and intergovernmental organizations having received a standing invitation to participate as observers."  For internet identification, the SMOM has neither sought nor been granted a top-level domain, while Vatican City uses its own domain (.va).

the capital "city" Palazzo di Malta in Rome

SMOM Licence plate

The Order has established diplomatic relations with 104 sovereign states.
The SMOM coins are appreciated more for their subject matter than for their use as currency; SMOM postage stamps, however, have been gaining acceptances among Universal Postal Union member nations.
The SMOM began issuing euro-denominated postage stamps in 2005, although the scudo remains the official currency of the SMOM.
Before : 1 Scudo = 12 Tari = 240 Grani (1 Scudo = 0,24 Euro).
Also in 2005, the Italian post agreed with the SMOM to deliver internationally most classes of mail other than registered, insured, and special-delivery mail; additionally 56 countries recognize SMOM stamps for franking purposes, including such as Canada and Mongolia that don't have diplomatic relations with the Order.
This means that the stamps of SMOS really are used, but the SMOM is not a member of UPU

Are stamps of the SMOM bogus or not ?
If you consider being part of UPU to determinate if a stamp is a real or fake, then SMOM stamps should be considered as bogus (cinderellas).
But if you consider stamps that are accepted by many states (56 is quite a lot) for postal use, then you can collect them with the knowledge you're collecting real stamps.

National Holiday is June 24.
http://www.orderofmalta.org/catalogue/stamps/?lang=en