A letter from Christine Miller of Annandale says: "I read with great interest your column of Nov. 20, in which you talked about Abernathy & Closther's 'diamond earring' offer. If only I had read it several weeks ago!

"I don't consider myself a sucker, and can usually see through advertisements for items that seem too good to be true. When I saw the Abernathy & Closther advertisement, I was skeptical; but I was also very curious and willing to spend $6 to satisfy my curiosity.

"I did not expect to receive the crown jewels -- perhaps some earrings of low quality but significant enough to give as a 'stocking stuffer' to some little girl who might get a kick out of having 'real' diamond earrings.

"As I said, I didn't expect much. But what I received first stunned and then angered me.

"I received a pair of earrings composed of some cheap metal. There was a setting of metal about the size of a karat, and inside that setting I thought I saw something sparkle, but it was so tiny I couldn't be sure.

"I moved to better light to try to find the diamond. There, inside the large metal setting, was what appeared to be nothing more than a grain of sand -- no larger, no brighter.

"I wasn't even sure that this speck was the diamond at all. I know, I know: for $6, what did I expect? Not much. But these earrings shouldn't even sell for $1, let alone $6."

Well, so much for that "advertising test." Christine indicates that what it really tested was her credulity.

Ann Sanders of Alexandria was also interested in my mention of Abernathy & Closther. She wrote:

"I have a jewel of a story to share with you. Unfortunately, it is not one to treasure, although I must say that the advice Caveat emptor (Let the buyer beware) is now one that I regard as good as gold."

In August, Ann saw an Abernathy & Closther ad in a Philadelphia paper. It offered a big bargain: afloating hearts made of 14 kt. gold, priced at $5 each, plus the usual $1 for "handling." Ann ordered two. Her letter describes what followed:

"The package arrived a few weeks later. It contained two tiny plastic boxes with foam cushions. I was astounded because I had to look very intensely to assure myself that the boxes were not empty! Finally, with the aid of a magnifying glass, I found the hearts. Now Abernathy & Closther has my name on their mailing list and I am receiving brochures for more bargains, outstanding values and incredible offers. Fat chance."

Douglas W. Harold Jr. of Alexandria was interested in an advertisement in The Star because its big, black headline shouted, "Buy a Gold Coin for $10, Call Toll Free by Midnight Tonight."

The carnival pitchman's timetested chant, "Hurry, hurry, hurry," remains almost as irrestible when it is reduced to writing. So Douglas looked more closely at the ad. It offered a "solid 14-karat miniature gold Krugerrand for $10" plus the usual $1 for shipping. The miniature coin was described as weighing .174 grams. Don't overlook that decimal point.

In calculating the per-ounce cost of the coin, Douglas began with the formula "1 gram equals .035 ounce," which relates a metric weight to an avoirdupois weight and yields, says Douglas, a unit cost of $2,805 per ounce for 24-karat gold. Needless to say, he didn't call the toll free number, either before or after midnight.

I am not familiar with either metric or avoirdupois weights for gold, but do know that the metal is usually bought and sold by troy weight: 12 ounces to the pound, 20 pennyweights to the ounce, 24 grains (not grams) to the pennyweight. The metric equivalent of a troy ounce is 31.103 grams, and by my calculations one who pays $11 for a 14-karat coin that weighs .174 grams is paying at the rate of $3,370 per ounce of 24-karat gold.

"There will be a limit of 10 miniature Krugerrands per address," the ad said. With pure gold available in unlimited quantities at about $640 an ounce, one is left to wonder how many thousands of people rushed to take advantage of an opportunity to pay $2,805 or $3,370 an ounce for it.

My only comment is that at around $3,000 an ounce, I'd much rather be a seller than a buyer.

The Better Business Bureau has been preaching for years that when you're offered a bargain that seems too good to be true -- it usually is.

The Better Business Bureau gives excellent advice.