Flag Identification???

[lavagna]

Good day Gents,
Could anybody help with the identification of the following flag.
It is stamped Signal flag, and as I have never seen one like this before, I would appreciate any info about it. Where and how was it used, how rare it might be, etc.
Thanking you in advance.

Regards
Bruce

[jmcm]

I believe its a Harbor pilots flag, Joe

[kp520]

Flag

Yes, harbor pilot flag.
Was flown by watercraft that guide a vessel in harbor, river ect.
Not rare, fairly common.