105mm Howitzer M314 Illumination round, early differences.

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Here is my 105H 1953 dated Illum projectile. Interesting notes, the fuze assy thread diameter is 1.7" as opposed to the modern 2.0". Early Illum rounds were colored grey with white. Modern era are white with black lettering. I am not sure when the thread diameter changed, but think the 1.7" was used prior to the 60's, later 2.0" fuze diameter type.

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Fuze. Nice looking round.

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Early and modern era fuze diameters.

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For the collectors, an added helpful note. "The fuze sizes for MOST of the US Artillery from 75mm on up for the treaded portion were about 2" measured from the tops of the pitch and with 12 threads per inch. There were exceptions to this rule when dealing with the WP rounds ( and gas, and illumination) rounds of 75mm, 90mm and 4.2". They were 1.7"x14 . For PD these would have been the M48 Series. Now, take that same fuze and add a booster adapter M21 series that has an arming delay and a healthy booster (gaine) on it and has the 2"x12 thread pitch, and you have the M51 series PD fuze. The Navy even used it in the Mod 3 version for 5" 38 Cal. " From the cartridge collectors website.

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More. From my fuze examples: left , 1.7" M44 dummy fuze, right standard 2.0" M557 PD fuze.