Could it be signature air services (quick google - sorry Signature Flight Support), the company that services private flights into/out of DCA (and other airports). Not that I've ever flown private, but I thought they had sort of scrolly (script) "Signature" logo. Indeed on their site,
https://www.signatureflight.com/Loca...o.aspx?Loc=DCA
there's a picture in the slideshow of an awning that appears to show that logo.
Either that or Jack Abramoff re-opened his Penn Ave eatery near DCA.