GOING once, going twice, gone! - 20 televisions, a used motor, and even an old sewer cleaner with one spare wheel and a protective screen. It is one of the best-kept secrets among bargain-hunters in Hongkong - a Government auction, where anything from redundant government office supplies to confiscated stolen or smuggled goods can be bought by the highest bidder. The auction is controlled by hammer-wielding manager of Hongkong Auctioneers and Estate Agency Ltd, Mr Andrew Wu. The hammer is traditionally used to indicate a sale, but judging by the excitement generated by squabbling bidders, it may well double up asa method of crowd control. Sales are fast-moving, and bidding escalates to such a fever pitch that the electronic display board behind the auctioneer can hardly flash up each bid before a higher one is made. Popular items are electronic goods like televisions, video recorders, stereo's and air conditioners - items that can be easily sold in Hongkong or exported to countries like Vietnam. Bargains bought at a recent auction from the list of confiscated items included a green sampan fitted with a 15-horsepower Mariner outboard motor, which went for $3,600, a lady's rolex for $14,900, several Honda motorbikes were sold for under $1,000. A lot of 39 Panasonic Televisions went for $83,000, and a set of of six Mitsubishi outdoor air-conditioners and six indoor air-conditioners fell under the hammer for $50,000. Need a spare part for a radar system? Look no further than the auction of goods no longer wanted by the Royal Observatory. The government supplies department can provide you with an unserviceable lawnmower, assorted hair-clippers, and a variety of unserviceable batteries. While the Hospital Authority offered 68 elbow crutches, five stethoscopes, a traction machine for the head and a ''vibrator'', the Electrical and Mechanical Services Department got $5,000 for their sewer cleaner. Half the price has to be paid in cash to the auctioneer upon fall of hammer, the remaining balance to be paid in cash the following day. Buyers have to register their ID card number with the auctioneer. Goods are stored at a variety of government stores across territory and can be viewed in advance. The auction is divided into three sections. Confiscated items are auctioned first, followed by unclaimed items, and then government materials. Auctions are bi-monthly. The next will be held on April 22.