To enforce rationing, the government issued various kinds of coupons to buy everything from needles to boxes of matches to grain foodstuffs to clothing to a then-luxurious wristwatch or bicycle - in addition to the money required to pay for it.

Today, however, as capitalism increasingly takes over as China's economic system, market supplies are abundant and the days of rationing have disappeared - and the coupons have become collectibles.

Nevertheless, at least in Beijing, the coupons are still necessary to refill cars' tanks at petrol stations run by the state-owned oil giant, China Petrochemical Corporation (Sinopec Group), which is the parent of Hong Kong-listed Sinopec.

The group's petrol coupons in fact are pre-paid purchase certificates and in this sense are different from others, which only specify the quantity of certain items that consumers are entitled to buy with cash. The petrol coupons are antediluvian products of the socialist rationing system and their survival is evidence of the state's monopoly on the petrochemical market.

Sinopec began to issue the petrol coupons in 1964 at a time when oil was a rare commodity in China. But then automobiles were also rare and owned only by government organs or state-owned enterprises, and as such all expenses were covered by public funds.

Under these circumstances, it was convenient for the government to match supply and demand and balance its budget with pre-paid coupons.

Incredibly, despite fundamental changes in the Chinese economy and society over more than the past two decades, Sinopec Group has continued to issue the coupons and its stations only accept such coupons as payment for fuel.

The only difference is that the coupons are no longer allocated by the government, according to budget needs. Instead customers must pay cash to buy them beforehand.

There are reasons that the old system has prevailed. It wasn't until the dawn of the new millennium that private cars gradually become available and affordable to mainland residents, and then ubiquitous. There has been no urgency to change the coupon system until recently.

But in addition, the coupon system also serves the state-owned oil giant's interests and is an attractive addendum to its business operations. The pre-paid coupons allow it to collect huge amounts of money in advance of retail sales.

It saves its petrol stations the trouble of cash transactions and transportation.

While a pre-paid coupon guarantees the supply of a certain quantity of oil product at a pre-fixed price, the risk for Sinopec Group has been nil as prices of oil products, tightly controlled by the government, have remained quite stable - until this year.

Sinopec is the largest oil retailer on the mainland. It operates 30,164 petrol stations across the country while its rival, PetroChina, runs 17,403. And in many provinces, Sinopec in fact monopolizes the market.

This leaves consumers no other choice but to buy the coupons if they want to use Sinopec Group's services. Lack of competition, harking back to the old socialist days, maintains this vestigial system.

However, sharply fluctuating international energy prices are motivating Sinopec to finally scrap the coupon system - but, again, in an apparent desire to safeguard its own interests.

The dramatic rises and falls of world energy markets have forced the central government to take a more flexible attitude towards price controls on oil products, allowing oil companies to make adjustments from time to time.

This means that selling petrol coupons at predetermined prices is akin to speculating in futures.

As oil prices tend to rise, they imply huge risk for Sinopec.

So the oil giant has reacted quickly to abandon the 41-year-old coupon system in one province after another.

Last week, it announced that beginning in 2006, all of its pre-paid coupons would cease circulating in Beijing - the last city in which the coupon system still works.

Nonetheless, Sinopec is refusing to refund any sold coupons, which naturally upsets savvy consumers who have foreseen the oil price rises and bought far more coupons than they could use in the remaining months of the year.

Still, consumer pain or no, Sinopec's move ought to be welcomed as a market-oriented tactic, as small a step as it may be, to rid the country of one more socialist influence.

In addition, Sinopec Group's scrapping of the coupons may open a new market for credit cards, debit cards and other electronic payment means, although it is certain that the oil company will itself take a big bite out of the cake.

The consumer has one faint consolation: those remaining coupons in their drawers should ultimately become collectors' items just like the rest of the rationing chits did years ago.