Hi. I am going through a batch of old cooking magazines and found
this ad for Borden's Eagle Brand Condensed Milk.

Magic Shaker Mayonnaise
Source: ad on p. 720, American Cookery Magazine, April 1930.

1/4 c cider vinegar
1/4 c salad oil
2/3 c Eagle Brand Sweetened Condensed Milk
1 egg yolk, unbeaten
1 tsp dry mustard
1/2 tsp salt, few grains cayenne

Place ingredients in a pint jar in the order listed. Fasten top
on jar tightly and shake vigorously for a few minutes. The
mixture will blend perfectly. If thicker consistency is desired,
place jar in refrigerator to chill before using.
--
Jean B.