Yes, it is hallmarked 1872. Nicole was inventor of both, the system for keyless winding as seen in this watch, and of the heart shaped cam for returning chronograph hands to zero. "Dent" is, as often, the trade agent "only". The basic movement, including the keyless winding, clearly is made in England. Interestingly the same kind of caliber is seen with and without the "partly Swiss" mark. One can only speculate that parts of the chronograph mechanism are meant therewith.
Here is another and earlier "Dent", which I have since decades, with the same keyless system and hallmarked 1856. In this case with duplex escapement. This watch is completely English made.
😉.