The Carrera 45 Dato...
Model 3147, and made by Heuer in the mid to late 60's was powered by the Landeron 189 movement. I can't verify whether Heuer manufactured the similar Titus watch you are looking at, but a matching movement may be a good clue. Hope this helps. If you are able to verify that Heuer made this watch, please let the forum know. Good luck with the purchase...it's a great looker!
Bob Keller
Should have included a link:
:
: http://www.ebay.co.uk/itm/Titus-Branded-Vintage-Heuer-Carrera-Chronograph-1960s-/161310287076?pt=Wristwatches&hash=item258ed7a4e4
: Cheers
: Steve