Strange frame stamps

[triracer67]

Putting bumpers back on and noticed four stamped characters on passenger side top of frame, just behind bumper, under grill. It appears as though it is GH M or GH 11. It’s a 67 U15, nothing special.

 

[Slowleak]

Mine has something similar. It’s a ‘77 and I see a portion of this is “D7” meaning “77”. It’s a part number or date stamp.