Decyphering Mold & Date Codes

Hemingray used mold letters, dome numbers, and even oddly placed periods in some of their earlier insulators to denote which mold an insulator was produced from. However, it wasn't until 1933, when Hemingray was purchased by Owens-Illinois, that they began embossing their insulators with specific mold and date codes. Many different codes were used from 1933-1940 until they settled on a single standard, and I will explain them all here in relative order.

In 1933, Hemingray was purchased by Owens-Illinois, and they began embossing an "O" on their insulators (believed to stand for the O in "Owens-Illinois".) The "O" is a smaller font size and is typically aligned either above or below the "N" in "HEMINGRAY" (with the exception of CD 137 and CD 142). All known specimens are Ice Blue in color. At least one specimen (CD 154) has also been found with a large mold number below "MADE IN U.S.A." on the rear skirt, though mold numbers are seldom seen this early on.

In 1934, Hemingray added a "_4" after the "O". The "4" is believed to signify the year 1934. Some specimens have also been found with a mold number on the rear skirt above or below "MADE IN U.S.A.", though mold numbers did not appear to be used consistently until 1935 and later.

In 1935, Hemingray added a period after the "4" and added mold numbers to the insulator, typically on the rear skirt above or below "MADE IN U.S.A." Each successive year the mold was used, an additional period was added above, below, or on either side of the "4". In this example, "12" is the mold number.

I believe this is the earliest form of the 1938 date codes. Similar to the 1934 date code above, the "4" has been replaced with an "8", signifying 1938. A period would also be added after the "8" for each successive year the mold was used. In this example, "12" is the mold number.

This is another version of the 1938 date code. In this version, they eliminated the "O_" and simply put "38" to signify 1938, again aligned with the "NG" in "Hemingray". A period would also be added after the "38" for each successive year the mold was used. In this example, "12" is the mold number.

This is another version of the 1938 date code. In this version, there is only an "8" to signify 1938, this time aligned with the "G" in "Hemingray". A period would also be added after the "8" for each successive year the mold was used. So far I have only seen this style of date code on the CD 154. It's possible this may be a modified version of Version B (above) with the "3" removed. In this example, "4" is the mold number.

This is a unique version of the 1938 date code. First, this type only appears on three Hemingray styles (CD 115, CD 122, and CD 155). Notice that the mold and date have been combined for the first time (in the example, the mold number is "23" and the date is "38"). What's also unique about this version is that the type is the same size as the main "HEMINGRAY-10" embossing on the front skirt, and "MADE IN U.S.A." was inexplicably omitted. In 1939, Hemingray added "MADE IN U.S.A." in smaller letters underneath the unusually large mold and date code, and added a period after the "38". Most of these molds were only used up until 1939, however I have found one mold that was used until 1940 (with two dots after the 38).

This version of the 1938 date code is a hybrid of Version C and Version D, where they combined the mold and date codes together on one side of the insulator, like in Version D, yet only used an "8" to signify 1938, as in Version C.

Identical to the 1938 Version E, using a single digit "9" to denote 1939.

Following the pattern of the 1939 version above, this version uses a single digit "0" (zero) to denote 1940. Do not confuse this with the original "O" (letter O) used in 1933! A 1940 "0" will always be found AFTER a dash and on the REAR skirt.

Similar to Version A above, a few Lowex and Hemingray molds were produced with this unique embossing. In this example, "512" is the style number, "1" is the mold number and "0" (zero) is believed to signify "1940". As with Version A above, do not confuse this with the 1933 "O" (letter O)! This particular version of the mold and date code is found only on CD 216, CD 230, and CD 299.7.

Thankfully, by 1941 Hemingray had settled on their final mold and date code standard. This can be found on all Hemingrays right up until they stopped manufacturing insulators in 1967. In this version the mold number is to the left of the dash, and the date is the two digits on the right side of the dash opposite the mold number. In each successive year a mold was used, a period would be added somewhere beside, above, or below the date. So, an insulator with a date code of "41:::." would mean that insulator was produced in 1948 (1941+7 dots). This can be found either on the front skirt below "HEMINGRAY" or on the rear skirt below "MADE IN U.S.A."