By Ellie Tzortzi

PODGORICA (Reuters) - For most European Union states, adopting the euro currency is the final step in a long and difficult journey through rigid membership rules and regulations.

For Montenegro, which signed its first accord with the EU on Monday and will need years to become a member, the euro has been a reality since 2002, when it adopted the currency unilaterally.

The euro sign is everywhere in the small Adriatic republic, from billboards advertising loans to cardboard price displays in vegetable markets, making it feel like any formal euro zone state.

Economists say that after teething problems in the first two years, its use motivated the government to apply sound fiscal policies and improved Montenegro's image, directly contributing to a boom in tourism and real estate.

"It's great they have the euro, it makes everything so easy, and it's stable," said Briton Marie-Louise Morrison, leafing through property catalogues in the medieval town of Kotor.

The picture was very different seven years ago. In late 1999, the rump Yugoslav federation of Serbia and Montenegro faced ruin after a decade of war and 78 days of NATO bombing to force Serb forces out of the breakaway province of Kosovo.

Montenegro's government -- not in any case in control of monetary policy, which was decided by Serbia -- weighed its options and decided to adopt the German mark, the currency of choice in a region ravaged by hyperinflation.

AIRLIFT OF HARD CURRENCY