I love these heirloom watches, I also have a Bulova I received from my father over 40 years ago. It will be the last watch in my collection.
This one is a dilemma. My first impression is that it's not a Bulova watch in that it doesn't have Bulova marking on the case. I do understand that it's possible that it was filled when the original personalization was 'removed' but it seems unlikely. We have not, to my knowledge seen any Bulova watches cases in Dennison cases and I suspect it might have been a marriage.
For now I'm suggesting this one is Non-Conforming (not all original Bulova signed components) although I'm willing to reconsider if comes to be known that Bulova used this case manufacturer.
Either way, the beauty of this watch is it's provenance. Congratulations on having this wonderful keepsake from your father.