Hello Walker,
Yes, I think your explanation makes sense.
The bottom edge of the side plate definitely is stamped "76" in the commerical style and in the same font as all the other small parts. When someone decided to strike "76" on the side plate surface I think they used stamps with a little different font style and they got the "6" rotated 90 degrees wrong with their first strike, then realized it, and corrected and struck again with the "6" in the 12 o'clock position.
<img src="graemlins/yltype.gif" border="0" alt="[typing]" />