Mustang Markings Question

[VaBeachEd]

Visitor to the Military Aviation Museum in Va. Beach asked "what does that black cross mean"? And I don't know! (I hate that!)
The good news is, I know who does know!! That would be the "Warbird Collective" -- ok, my fellow warbird nerds, over to you for help. What the heck does the black cross on the bottom of the ID stencil on the P-51 mean? I've seen it on lots of other aircraft and never gave it a thought.

[Richard W.]

Signifies that the a/c has been fitted with the extra internal 85 gallon gas tank in the fuselage.

[VaBeachEd]

I knew someone from "the collective" would know! Thanks!

[DH82EH]

That response time of twelve minutes leaves a little to be desired though

Seriously, well done WIX

Andy

[CraigQ]