Looking at a number of photos, it is still unclear whether all models used periscope guards. My references of M4A1's do not show any evidence of the guards, and even on later models some had them and some not.
Were they standard equipment on the earlier models?
No, periscope guards began to appear in late 1943. By 1944, they were standard on new equipment. Older tanks did not have them, but could receive them during rebuilding, along with other improvements like new cupolas and the wider M34A1 gun mantlets. Gerald Owens
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