It’s rare that these old furniture pieces made by our favorite cabinetmakers are marked so as to let their origin be known. It requires a learned eye to spot the details and to discern that a piece was made by one maker or the other; even then, however, one can rarely be 100% sure, nor should be sure.
For Herter Brothers pieces, one of the gimme signs is the “H” key. Although I’m not sure anyone has done the proper research to be sure that the Herters were the only makers who had an “H” symbol on their keys, it is common practice to use this as a probable sign that their piece is a Herter piece, whether 100% surefire proof or not.
Another sign is the presence of casters by India Comb Rubber. Per the Herter Brothers book, a large quantity of original casters survive on Herter Brothers pieces and, “In what sounds today like hyperbole, the company advertised in 1864-65 that ‘solid Emery Vulcanite wheels … [resembling] stone or iron, will wear out hundreds of ordinary wheels.’ Time has confirmed this boast.” I personally doubt that Herter Brothers solely made the payroll for India Comb Rubber Co., but their wheels were certainly used by Herter.
It is not unthinkable that someone could take these two items and put them on any cabinet of upper-end quality and pass it off in some circles as being a Herter piece without being questioned. Just this weekend I was talking to a Victorian furniture dealer who said that he had a customer that told him about a Herter Brothers cabinet that he bought for $3,500 at an auction. Highly unlikely that it was a true Herter at that price point, but not out of the question.