But there are more surprises, say those in a position to know.

Among the bidders, the South China Morning Post was told this week, is a multinational banking group. Also - Chinese and Taiwanese bidders apart - there are a surprising number of Hong Kong bidders in the frame. And the reserve price placed on the business and conditionally accepted by those bidders (ahead of their due-diligence investigations, which are now under way) was fractionally above twice its book value.

Based on the 2004 full-year results of listed Asia Financial, the group's book value was $3.4 billion, with Asia Commercial valued at $1.69 billion, the group's insurance business valued at $1.1 billion and its corporate and investment business at $641 million.

That produced a book value per share of $3.24 for the holding company and $1.60 for the bank.

Full-year results are likely to leave the book value of the bank at $1.8 billion or so at the end of last year, and assuming due diligence proceeds smoothly, at least one of those 12 bidders may comfortably be expected to fork out the $3.6 billion or so that the vendor wants. After all, why bother to proceed with the costly business of making a bid if you are not willing to meet the reserve price?

Signals sent this week suggest the parent will settle for no less, preferring to continue running the bank itself rather than part with the asset below the target price.

Of course that could be no more than the entirely expected brinkmanship, and having run through the numbers, the bidders would be justified in putting in bids well below the reserve price.

Yet if they had pinned their colours to the mast with a price that high Asia Financial's management would have a tough job emerging with their credibility and acumen intact if they were to accept a price closer to the 1.15 times book value bandied about in the market.

So expect a multiple closer to two times book value than the figures around 1.15 that have been suggested by the more pessimistic commentators.

And the timing appears to be on Asia Commercial's side.

The most recent big test of valuations in the market came with the initial public offering in October last year of China Construction Bank Corp. Priced eventually at a multiple of 1.9 times book value, the outcome was well ahead of multiples to which bank assets had fallen in recent mergers.

Of course, the two are hardly comparable. The smallest of Hong Kong's banks, Asia Commercial had assets of just $14.3 billion at the end of 2004 and produced a pretax profit of just $98 million.

Leave aside the passage of time since those mergers and given the new-found muscle being flexed by mainland banks, that is a profile that by rights might have earned Asia Commercial a sale at a multiple of not much more than the 1.05 times book value that was fetched in the sale of Fortis Bank to ICBC (Asia).

But times are changing. Asia Commercial's 12 Hong Kong branches may be inconsequential to local bidders (which makes one wonder what has driven the interest from domestic banks), but could be very attractive to mainland banks on the expansion trail in Hong Kong (read China Construction Bank and ICBC). Asia Commercial's representative office in Taipei would be an added lure for mainland banks wanting a slice of the growing business of financing cross-straits trade.

Asia Commercial has just one full banking branch on the mainland, in Shenzhen, and only representative offices in Shanghai and Shenyang - small beer for Hong Kong banks such as Bank of East Asia, which has 13 mainland branches, including one in Shenzhen (why then, the rumoured interest?) - but an added attraction to Taiwanese bidders hoping to overcome political hurdles and expand their business into China.

Small it may be. But the owners of Asia Commercial believe the remaining window of opportunity for bidders to grab a low-cost foothold in the mainland market is just as small.