The men are of nondescript appearance, with clothing that marks them out perhaps as a traveler, perhaps a laborer, but nothing so exotic or fine as to draw speculation. Depending on your activities in the waning hours of the evening, one of the men might sidle up to your spot at a bar, or perhaps be standing behind you in line at a shop -- maybe even simply approach you in the street in between destinations.
The conversations are similar: each of you is greeted politely, and each man introduces himself as Cortland, a colleague of Dr. Serabel's. How he knows of your association with the Applicator is left unsaid, but you may be able to deduce that he spotted you in the Ha'penny Pie, and must have followed you thence. Cortland offers each of you a small artifice which he calls a locator -- the lumen powered device is similar in size to a snuff box, and is little more than a metal box with a hinged lid, inside of which is the lumen crystal embedded in finely wrought glyphs, and a small button. Depressing the button, Cortland reveals, sends a wide-ranging lumen wave at a specific frequency which can be tracked via his receiver.
Depress the button once a day to reveal to him the airship's location, and you will be rewarded 500 marks, in addition to whatever you receive from Dr. Serabel herself. With that simple pitch as his job offer, Cortland makes to depart, leaving behind the locator and a small coin purse with five golden monarchs.
MISSION #001 COMPLETE!