This is a Welch 1259 large classroom thermometer. It's quite large, the spirit tube is 24 inches long. The scale ranges from -40 to 122 Fahrenheit, with an adjacent Celsius scale. It's listed in the 1963 Welch catalog, and shown in the 1968 Welch catalog, available on this website, so it probably dates from the 1960s or 1970s. The 1968 catalog shows a somewhat different scale, however.

Go to Welch catalog page.

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