This is the AEG (Allgemeine Elektricitäts-Gesellschaft) desk clock model 'BUT' made in the early 1970s, not the 1960s as sometimes said. The clock is a design classic by clock and watch designer Kurt M. Traeg, who worked for Kienzle from 1964 before doing freelance design for various clock companies including VDO, Haller, Hermle, and Kundo.  

Kurt Traeg undertook some training at the Bauhaus school.  Though he did not work for the Bauhaus, but that experience probably influenced this very minimalist design.  It was made in either black or very dark, almost black, green with clear perspex and some have an aluminium silver sheet between the clear and black plastic around the dial (as in the pictured clock, which is also the very dark green). Traeg was a master of design in plastic and also designed the Kundo spacetimer in 1986 and other classic plastic clocks. 

However, the design is not only in the outer appearance. The BUT clock contains the revolutionary W627 transistor controlled balance movement designed by Traeg in conjunction with the Kienzle horologists.  The movement is almost entirely plastic and made without screws.  There are three flat plastic plates containing the train, balance and electronics held together with rubber O-seals.  The modular design allowed the movement to be stripped and faulty modules replaced in seconds, and also reduced manufacturing costs by separating out different types of manufacuring processes into only one of the three modules.  Various movements were made.  The BUT contains the 'baby' model and there were other sizes, some later types with strike and some with 'pendulum'. 

The W627 is a design classic and was hugely successful, with 11 million baby and mini movements sold in 10 years until quartz made it obsolete and production stopped in the early 1980s. Unfortunately, the BUT clock was not so successful.  Its avant-garde design, the  price for a quality product and the idea of a plastic clock were all new and sales were poor.  This earned the BUT clock the nickname of 'tombstone' in the company.  Now, this combination of design and rarity make this a very desirable item for modern collectors. 

The clock is very small, only 65 x 55 x 80mm and runs on one AA 1.5v battery.  The second hand movement is very smooth, almost a full sweep seconds. It utilises two silicon transistors, most other ckocks of the period using a single germanium transistor. An accuracy of 1 second a day is claimed.

The circuit board and component layout are very similar to that used in later Kienzle car clocks.

Further reading:

Uhrengestaltung (clock design) im "Plastic Age". Der Designer Kurt M. Traeg by Johannes Graf in the Annual journal / Deutsche Gesellschaft für Chronometrie , Vol.57.2017, pp. 79-92, 2017.  Article in German. ISSN: 1617-0113

Article on the Kienzle W627 by A. Haag, in Uhren Juwelen Schmuck (Uhr) Vol： 31 Issue： 11, p25-28,30,32 (1976) in German.

EWO