And for 25 cents extra . . .

For $82 you can get a book called ''Rainy Days at Brig o'Turk,'' a sketchbook of the great Sir John Everett Millais. Apply to the Dalrymple Press, Westerham, Kent. No need to mention my name as they never heard of me, but I have heard about Sir John Everett Millais, and I'm pleased to learn his 1853 sketchbook is in such booming prosperity. It happens I have a Millais gracing my bedroom wall. True, the Tate Gallery in London has consistently refused to acknowledge that Sir John ever painted ''Little Sweethearts,'' but I know better. Mine is one of several million lithographic copies turned out in the 1890s as a magazine subscription premium, and ''Little Sweethearts'' was the greatest circulation gimmick of all. ''Little Sweethearts'' was one in a long series of pop art offered as circulation come-ons by the Family Herald & Weekly Star of Montreal.

The picture (suitable for framing) shows a lad and lassie and a basket of wild strawberries, enough so it was described as ''sweetly sentimental.'' Mine was given to me by Jane Acorn of Prince Edward Island, a girlhood chum of my mother, and Jane had had it since her father had renewed his subscription and included 25 cents extra for the picture.

Jane asked me if I had ''Little Sweethearts.'' No. ''Would I like 'Little Sweethearts'?'' Yes. Jane well knew that the picture brought a fancy price and that while millions had been in print few, for some reason, existed. It always amused, and pleased, her that I paid $25 to have the 25-cent picture framed.

In an era of fierce magazine competition, the subscription premium was not always a picture. The New England Homestead used to give away a pair of Norway maples - the red ones - and wherever you saw red maples flanking a front door you knew they took the New England Homestead.

The Family Herald & Weekly Star stuck to pictures and promoted them so well they had to maintain a mailing office in Boston to save money on postage to the States. When they arranged for a picture, they would begin to tout it and carry along with weekly reports of progress.

Some of their other pictures were ''The Battle of Balaklava,'' ''It Fell From the Nest,'' and the montage celebrating Queen Victoria's diamond jubilee. ''It Fell From the Nest'' showed a child holding a fledgling while gazing up into a tree. They also offered the portrait of Sir Wilfred Laurier, Canada's first French-Canadian prime minister. Laurier and Queen Victoria are still found in many Canadian homes. But ''Little Sweethearts'' for some reason began to disappear soon after many million copies were distributed and today is hard to find.

The Family Herald & Weekly Star ceased to publish some years back and ended a long service as Canada's leading family magazine. When it was still publishing, I went into the offices in Montreal and inquired about ''Little Sweethearts.'' I was promptly led into the office of the editor (who was not in) and shown a framed copy of ''Little Sweethearts'' on the wall over his chair. The assistant who had thus favored me said, ''Since you came in to ask about it, I think you must know more about it than we do!''

The story behind ''Little Sweethearts'' had been lost in the years. But the files revealed that ''Little Sweethearts'' had been done by the great Millais and was so advertised at the time. Until then, the promotion blurbs said, good lithography had been done only in Germany, but now a firm in London, Low, was competent and was doing ''Little Sweethearts.'' Issue after issue, progress was reported, until the first shipment had been made and the vessel had at last docked in Montreal. Clerks began counting quarters.

The Tate kindly answered a query but said there was nothing about ''Little Sweethearts'' in the Millais story. My guess: He did it as a bread-and-butter job and didn't bother to sign it. Or perhaps he felt he was demeaning himself by crass commercial contacts in that awful America. No, I think I will not send $82 for a copy of ''Rainy Days at Brig o'Turk.''