According to Brooks Palmer, (A Treasury of American Clocks, 1967, p.277 and p.338) here is what we can tell you about this firm:
The New Haven Clock Company originally made these Dickory, Dickory Dock Clocks, c.1910 under contract for the firm of Dungan and Klump; that would be Elmer E. Dungan and Charles M. Klump who did business at 1208 Chesnut Street in Philadelphia between 1909-1912. They apparently made three models of this clock in the New Haven factory, and a fourth in the Sessions factory under a 1910 patent. They also made some miniature models.
Elmer Ellsworth Dungan (1862-1930) of Flowertown, PA was, “a self-taught, self-made inventor.” He (must've loved younger women!) married Margaret E. Murray (1893- ). Listing an address of Fort WAshington, PA in 1909, he received patent no. 912-833 for a “mouse clock”, subsequently known as the “Dickory, Dickory Dock Clock”, or the “Dickory, Dock, The Mouse Ran Up The Clock” clock!
Dungan's Original “Mouse Clock” Patents:
There are a couple of quickly noticeable differences between models 1 and 2. First is that, on the earlier model, the front hinged open on the left side; on the older model it was screwed on from the front. Second, the style of numerals on the front is different between the two models. Many of the original clocks (most we've seen) are missing the original tail; it must've been very fragile, and certainly was “hanging out there” to be bumped and broken off.
What you have to watch out for are the knockoffs made by Horolovar and especially watch out for the Chinese knockoffs. There are lots of both of those available in the marketplace, but try and find one of these originals! It's like a lot of other things in clock collecting: know what you are buying and from whom you are buying it; caveat emptor!