In 1904 Waltham made a number of movements for the new E.Howard Watch Co. (owned by the Keystone Co.). These were made for Keystone until they finally got their own movement production under way in the old United States (Waltham) watch factory. The Waltham-made movements included bridge model watches and 3/4-plate models. The bridge models were based on Waltham's American Watch Co. grade, but the 3/4-plate was a new movement in 16-size. This is one of the first 3/4-plate models, having 17 jewels.

and here is the front of this watch.

Another contract with Keystone for more watches included this 19-jewel version in 1905.

... and one of the styles of dial that came on these watches -

Keystone finally had all of their own movements under production (3/4-plate and bridge style) by around 1907 and Waltham's attractive 3/4-plate layout apparently languished until several years later when it was revived for their Equity model and some export models, such as the Traveler.

This is the 12-size version, also made in 1904. Unlike the 17-jewel 16-size made at the same time, these did not have an "H" prefix to the serial number.