I serviced a couple Hamilton 950s last month and a Howard Series 5 today...

They are amazingly similar.

And the 950

21 jewels model 9 grade 107 Burlington looks like 950 Hamilton and I found them to keep very accurate time .

E. Howard became effectively Keystone Howard in 1903, and Keystone Howard was purchased by Hamilton Watch Company in 1930. Perhaps some engineering was transferred as well somewhere along the way.

KH

These "True Bridge" movements shared the same layout from early on. They were an early way to overcome some issues with the older full plate stuff, but were (themselves) fraught with fitment issues, making them more expensive to control. As Hamilton settled on the 992b as their "ultimate" mechanism, I would expect there was little exchanged to Hamilton besides the US Watch of Waltham/Howard/Keystone machinery.