THIRD PERIOD - SYSTEM MENGE
World” saxophones from the third period were stamped: “copyright 1938 by Herb. Menge Dresd. 28”, although I’ve seen several without the stamp.
This so-called system Menge makes it possible to open the high D (split mechanism) with the regular left hand palm key and close it with the C or B key in order to make trillers / bindings in combination with the high D, like D-C, D-B, D-A, etc.
Besides that you can grab a G# and by using the left hand middle-finger only, a Ab-Bb triller / binding arises. Other bindings in combination with the Bb are possible too, like G-Bb, F-Bb etc.
Horns without the stamp don't have this second possibility.
Officially the Herbert Menge copyright dates back to 1931. It was implemented in 1938 by FXH for their latest ''World" saxophones. The beginning of the third period.
The left hand pinky cluster on the “World” models was further improved with a bigger roller on the B flat key and the B flat/C and high E right hand side keys were now all curved topped and shaped like a stairway.
The third Period contained four models: ''Champion'', ''World'', ''World Super'' and ''World de Luxe''.
The “Champion”, the new basic model in this third period, had a two-ring micro tuner, a small left hand pinky cluster, no front F key, no extra triller keys and a second type body-to-bell brace (see pictures).
The “World” had a three-ring micro tuner, front F key, G-G# triller key and a high D system Menge key.
The “World super” was like the “World” plus a low D-D# triller key (alternate fingering C-D#) and a two-ring micro tuner.
The “World de luxe” was like the “World super” plus a high D-D# triller key, a little roller on the Bb key, a three ring micro tuner, custom engraving, and a full mother of pearl treatment. 
The system Menge saxophones have a VO-shaped body-to-bell brace and ocassionally a v-straight shaped body-to-bell brace (see pictures).

Tobi, a German collector was so kind to send me copies of a 1939 FXH cataloque, see the 13th, 14th, 15th and 16th row, below.

first and second row: World tenor, system menge explained
third and fourth row: World de luxe ( Luxus ) alto
fifth and sixth row: Hess tenor ( FXH stencil ), same features as the World model plus an extra low D-Es triller key / body to bell braces
seventh row: Hess alto ( FXH stencil )
eigth row: the Melody tenor ( FXH stencil )
ninth row: World tenor
tenth and eleventh row: World Super alto, custom ordered with an extra high D-D# triller key and a roller on the little B-flat key
twelfth row; World alto with modern key guards
thirteenth row: pic 1 to 4 Regent baritone saxophone ( FXH stencil ) / pic 5 1939 FXH cataloque / pic 1 to 4 source eBay.de / pic 5 source Mönnig Company ( V. Schindler )
fourteenth to sixteenth row: 1939 FXH cataloque source Mönnig Company ( V. Schindler )
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