The Murer strut folding cameras have a very idiosyncratic classification, and to complicate further this does not hold during the entire span of the different series. This specimen belongs to the F series, which corresponds to focal plane strut folding cameras with cross and rise movements. The shutter speed range (1/31 minimum speed) shows that it was made before the new shutters delivered from around 1925. According to the available catalogues this 13 x 18 cm model was made between around 1908 (at the time called model 14273/5) and 1916 at least. From 1926 only the format 10 x 15 was made for series F.
The body is made of wood and aluminum covered in leather. The viewfinder folds laterally on the body. The focal plane shutter is a Murer, delivering speeds in the range 1/31 to 1/1000. The non-self-capped shutter has constant tension, and the speeds are set by slit width, which is controlled from outside but checked on a scale on the internal back side (real speeds values inscribed and not slit width).
The lens is a Murer Anastigmat 'Primus' with a focal length of 180 mm and maximum aperture of 7.5.

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At Murer and Duroni, Klapp cameras are divided into two major families: those with a focal plane shutter and those with a central shutter. They are then classified using a nomenclature consisting of 2 to 4 letters or numbers.

Focal plane shutter:

First letter		Second letter				Third and fourth letter
D	Fixed front face	U			4,5 x 6	2	Anastigmat	Murer	f/7
F	Platine avant à décentrement	N			6,5 x 9 ( O from 1914)	M	Anastigmat	Murer	f/6,5
		L			9 x 12 ( E from 1920)	T	Anastigmat	Murer	f/3,6
		C			9 x 14	E	Anastigmat	Murer	f/5,5
		K			10 x 15	R	Anastigmat	Murer	f/4,5
		H			13 x 18	0	Aplanat	Murer	f/8
		W			45 x 107 mm (Stereo)	Si	Anastigmat	Koristka Sideran	f/4,5
		S			6 x 13 (Stereo)	Ke	Anastigmat	Koristka Equator	f/5,5
						Ka	Anastigmat	Koristka Meridian	f/6,8
						K	Anastigmat	Koristka Doppio Gauss	f/5,5
						3	Anastigmat	Goerz Dagor	f/6,8
						4	Anastigmat	Sintor	f/6,8
						B	Anastigmat	Berthiot Olor	f/5,7
						S	Anastigmat	Suter	f/5
						L	Anastigmat	Roussel	f/4,5
						Z	Anastigmat	Zeiss Iena	f/4,5
						1	Anastigmat	Zeiss Koristka Tessar	f/6,3
						5	Anastigmat	Primus	f/7

Central shutter:

First letter		Second letter		Third letter or number
U	4,5 x 6	L	Plate (simple)	0	Aplanat	Murer	f/8
N	6,5 x 9	F	Film-pack	2	Anastigmat	Murer	f/6,8
G	9 x 12	G	Film	3	Double anastigmat	Goerz Dagor	f/6,8
W	4,5 x 10,7  (Stereo)	P	Plate and film-pack (premium)	M	Anastigmat	Murer	f/6,5
S	6 x 13 (Stereo)	T	Plate (economical)	S	Anastigmat	Suter	f/6,8
I	6 x 13 panoramique	M	Plate (metal)
A	4 x 5
O	4 x 6,5

Klapp cameras with a central shutter can come in three different finishes: economical, standard, or premium.

In the "economical" version, the body is made of alder wood and covered with imitation leather. The viewfinder is integrated into the front plate. The shutter offers only P (Time) and I (Instant) settings. The shutter is of the sector type. The metallic parts are oxidized. Its lens is achromatic. There is only one model of this type, which is a UT.
In the "standard" version, the body is made of aluminum and brass covered with morocco leather.
In the "premium" version, the body is made of aluminum and covered with morocco leather. A mechanism allows for moving the front plate forward to focus from 1.5 meters to infinity. The viewfinder is mounted on the sliding lens cover. The shutter speed can be adjusted to 1/25, 1/50, and 1/100.

(source Malavolti)