Firmalampen were first produced by workshops in the Po Valley in northern Italy. Broadly diffused since Flavian times in Gaul, Britain, Germany, and central European provinces, they were soon imitated and produced locally in these areas. The lamps have a sturdy biconical body and flat outward-sloping shoulder, separated from the flat-bottomed discus by a raised rim. The plain shoulder features two or three square lugs symmetrically placed on both sides of the lamp axis. Some are pierced, a reminiscence of a former, abandoned function when those lugs (three or two) and the handle served to hold three suspension chains; these chains were joined at one end with a ring or a hook, as can be seen on bronze lamps with still-extant chains. The circular base generally has two rings, a bigger outer one and a thin inner one. Many bases have a workshop signature in relief capital letters, hence the appellation of Firmalampen. Three different individualized shapes of nozzles determine three types:
- In Loeschcke type IX the cylindrical nozzle has a beveled top and a rounded flat tip. Three variants in this type have been distinguished by Buchi 1975: Buchi IX-a, IX-b, and IX-c. In Buchi IX-a and IX-b, the discus rim is continuous, and there is a groove on the beveled nozzle top between the discus rim and the flat raised nozzle tip. This groove can be very narrow and shallow like a capital letter I (Buchi IX-a); or it can be much deeper and broader (Buchi IX-b, which is more common). In Buchi IX-c, the discus rim is interrupted by a V-shaped channel on the axis of the beveled nozzle top. This channel does not communicate with the wick-hole area, which is on a higher level.
- In Loeschcke type X the discus rim is prolonged to the nozzle tip, surrounding it and forming a broad channel, which communicates with both the discus and the wick-hole areas; this corresponds to Buchi variant X-a. From the Aquileia material Buchi has distinguished two more variants: Buchi X-b and X-c. The lamps in Buchi X-b are coarser, with rounded shapes; the sides of the nozzle neck are rarely slanted. Those lamps are executed in a poor-quality clay, sometimes slipped. The base usually has only one ring. Buchi’s X-c lamps are of even worse workmanship; rarely slipped, they have a blurred relief, a nozzle channel of varying width without an air hole, and the plain base, exceptionally marked off by one ring, is oval.
- Finally, there is a rather rare variant of Loeschcke type X, his type X-Kurzform, which corresponds to Buchi’s tipo X forma corta, whose main distinction is its short nozzle and wide shallow body.
Bailey states that the north Italian lamps of Loeschcke type IX started under Vespasian and were produced until the end of the first century A.D. (Bailey BM II, p. 274); in the European provinces copies continued to be produced until the end of the second century A.D. Loeschcke type X began ca. A.D. 90 and lasted until the end of the third century and even much later (Buchi 1975, pp. 29–33; Bailey BM II, p. 272). Bailey stresses that “there is no evidence for dating the cessation of manufacture of the Type in north Italy, and the situation is complicated by the difficulty of distinguishing, in many cases, between north Italian and provincial examples in many publications” (Bailey BM II, p. 275). In Pannonia, according to Iványi, local workshops continued to produce Firmalampen, sometimes much degraded imitations, until the fifth century A.D.
Apart from the Po Valley—where FORTIS, the most prolific and best-known workshop exercised its activity—Firmalampen were produced also in central Italy, as cat. 448, signed LMADIEC, probably proves. Very numerous in central European provinces, Firmalampen are scarce in southern provinces such as Spain, Sicily, Sardinia, Africa, and in Greece and the eastern Mediterranean. Out of sixty-four examples recorded in Algeria, only three seem to be imported north Italian products; the rest are locally made imitations, sometimes quite far from the original models, as shown by Bussière subtype C VII 1,c or C II 2,b (Bussière 2000, p. 85).