Lego logo on old space helmets?

[JayFigsss]

I have recently checked my light gray spaceman helmet and am surprised to see it only has the number "4" on the inside. Is this normal for something this old? I bought it off a reputable seller on Bricklink, so I believe it is genuine. I know some castle helmets don't have the logo as well, but I wish to confirm if the space helmets, specifically part number "193a2" on Bricklink, are the same as well. Would appreciate it if anyone who has an actual one from the older castle minifigures could confirm it. Thank you!

[Stereo]

They weren't as consistent with the logo back then, so probably normal.  I checked mine with the thin chinstrap and a red one has "3", yellow has "04 1".