During the twentieth century, technological developments meant that the temperature of ovens could, at long last, be exactly regulated. As a result, the old terminology for oven temperatures had to be translated – but not every cookbook or recipe got around to that. Some, however, provided helpful information on how to determine oven temperature. Here’s the one from “Pet Recipes” (1931), with bonus notes for those whose ovens don’t have temperature regulators, plus deep-frying temperature information:
250 to 350 degrees F. Slow oven
350 to 400 degrees F. Moderate oven
400 to 450 degrees F. Hot oven
450 to 550 degrees F. Very hot oven.
“The Co-Op Cook Book” (1942) provides the same numbers, with a variation on the flour test:
“The New Home Cook Book” from 1926, on yet another hand, provides directions with reference to rotary dials with numbers on them – “Put Food in Oven When Thermometer Hand Reaches” X, and “Suggested Cooking Heats. Set Adjustable Hand at” Y. It actually refers specifically to the Westinghouse Electric Range models M-1 and M-2 (wish I could find a picture of one!).
Now, a range of 50 degrees or more is not as precise as the modern cook expects. I’d probably try the lower end of the range to start with, as it’s easier to correct under-cooking than over-cooking.