Montblanc-Simplo supplied unbranded fountain pens via the firm Excelsior to retailers who could provide them with their own lettering, e.g. Adler & Co. In the concrete case of the Adler Spezial examined, feed with lamellae, the front part of the rod and the thread of the mechanism speak against Montblanc production. Similar Waterman-style models were also made by Diplomat, Tatra and Stöffhaas, partly with double spindle; on Montblanc simple spindles dominate. A safe attribution is only possible by disassembly and inspection of the inner workings, possibly after a brief bath in distilled ultrasonic water with attention to the risk of oxidation. Not every sub-brand pen with a Montblanc nib is from Montblanc production.