I ran dbdoctor on it...here is an updated .brd file
I also did manage just now to run Allegro2Altium.bat after adding extracata.exe path to system variables...it converts the .brd binary to .alg ASCII...and I've opened that in Altium 19.0.15...it's kind of a mess...might have to play around with layer mapping...
Hopefully you'll get a cleaner import if you have Allegro installed
And thank you, thank you, thank you for your time...I've been screwing around with this on and off for days