Close your eyes. Would you be able to tell the difference between a $5 note and $20? Would you be able to distinguish the value of coins from their different weights?

This is the challenge that blind and visually impaired people face everywhere and which they tend to overcome by getting to know the size, shape and feel of different notes and coins.

So, when 12 countries of the European Union jettison their national currencies in favour of euro notes and coins next January, hundreds of thousands of people will have to learn the feel of the new money they will use. Their ordeal will be compounded by the fact that, in most countries, the old and new currencies will co-exist for a period of two months.

The circulation of two different sets of notes and coins is expected to sow a lot of confusion, and nowhere more so than in Spain, where the National Organisation of the Blind (Once) depends on a salesforce of 22,000 blind people to sell the lottery tickets that fund the group's activities.

El cupon de la Once is the most popular lottery in Spain. It rakes in Pts420bn ($2.2bn, E2.53bn) a year, which allows the organisation to be one of the most dynamic in Europe.

The organisation's research foundation has developed mini-computers with a special Braille keyboard and Braille reading strips instead of screens. It helps blind students through school and university. The foundation is also working on a global positioning system tracking device that will eventually allow blind people to walk without sticks.

The introduction of euro notes and coins therefore poses a dual challenge for Once: as a lottery business, it must ensure it suffers no dent in revenues in the first months of the euro's existence. As a charitable foundation, its main priority is to familiarise some 70,000 blind people in Spain with the new currency.

Carlos Ruben, Once's deputy director-general, has been at the forefront of the organisation's efforts to prepare for the euro upheaval. His involvement has ranged from discussing the design of euro notes and coins with European Central Bank officials to working out the psychological impact of selling euro-denominated lottery tickets.

"Our big draws on Fridays have prizes worth Pta500m. It is an impressive figure. But when you translate it into euros . . . well, E3m doesn't sound so grand," Mr Ruben says.

Because the euro was fixed at Pta166 when Spain joined the euro-zone in 1999, the first salary checks and pension receipts following the change to euros will also appear modest in comparison with the familiar peseta sums.

"I think Spaniards will be nervous at first," Mr Ruben says. "They are likely to curtail spending for a few months until they are confident they can handle their household budgets in euros. This is likely to have a big impact on consumption, particularly on non- essential items like lottery tickets."

To make Spaniards familiar with euro lottery wins, Once is planning a special draw on August 15 that, for the first time, will be denominated in euros. Once will offer up to Pta1.6bn in prizes, which, conveniently, amounts to almost E10m.

Once's educational campaign will begin this month, when the ECB is expected to deliver copies of euro notes and coins.

"The ECB is particularly wary of bona fide notes and coins falling into the hands of forgers, so we will get replicas that will allow blind people to feel the weight and size of the new money, but that will lack certain details, like the imprint on the face of coins, which is not so valuable for us," Mr Ruben says.

There is much to do in a very short space of time. Over the next four months, a team of 700 educators will fan out across the country to teach blind people how to recognise the new money. To help Spain's blind people work with the currency, Once is seeking funding for talking currency converters. It has also ordered plastic moulds that will allow blind people to measure and identify the size of different notes, as well as slot machines for the new euro coins.

What most worries Mr Ruben, however, is the two-month transition period in which pesetas and euros will remain legal tender.

"We lobbied the ECB and the Spanish government for the transition to be as short as possible," he says.

"At first it was going to be six months, then three, and now, finally, two months. For blind people, this is far from being an ideal situation, as our lottery vendors will have to handle both currencies from day one. But we accept that the government had to take other considerations into account."

As for the lottery, the only question is whether Spaniards will be happy counting their prizes in millions of euros rather than billions of pesetas. All those extra zeros will be missed.