Friedberg, a district of Augsburg on the east side of the river Lech, used to be an independent city. Its horological fame was far below Augsburg's. Being resourceful, Friedberg's watchmakers decided to advertise their substantial talents to makers in other countries. They would make any watch, in any style a client would like, including engraving the client's name. Those clients included some well known British and Dutch watchmakers.
Of course, they also sold some watches under their own names, in their own country. Signing them "Lekceh London", did not mean they would export them to London, but rather it was to sell them with extra profit, due to the superior reputation of the British watches at the time.
There is little doubt that "Lekceh" must come from Heckel. The problem is that there were many Heckels in Friedberg; Johann (born on June 9, 1673), Franciscus (ca 1680-ca 1730), Franz Elias ("a watchmaker's son), another Johann (1721 -?), Michael (ca 1710-?, who possibly moved to Vienna), and yet another Johann who moved to Warsaw, Poland. There were also Heckl, Hekel, Hekhel, Hekl.
The watches signed Lekceh, London I have seen spanning from circa 1720 to circa 1770, strongly suggesting that the name was used by more than a single watchmaker. Abeler, in his monumental work on German watchmakers, agrees that Lekceh must be considered Heckel spelled backward, but adds that Franz-Joseph Häkhl also used the name.
There are quite a few Lekcehs around, some in magnificent cases, some relatively simple. The minute repeater, which was in The Time Museum, is the most important. The Belgium Royal Museum of Arts and History has a Lekceh with a similar movement to yours. Below is a photo of a time-only Lekceh from La Chaux-de-Fonds Museum.
Since your watch is a 7.5-minute repeater (do not mix up 7.5-min with a half a quarter), in all likelihood, it came in a very nice decorated gold case.