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.
The 1st Herbert Menge copyright: DRGM 1199967 vom 13-03-1931: ''Griffweise U. Mechanik für Holzblas-und griffvewandte Instrumente'', Herbert Menge Dresden.
The 2nd Herbert Menge copyright: Menge, Herbert,* Dresden, Germany. System Menge; einheitssystem für holzblasinstrumente und saxophone. © Aug. 15, 1938; A-Foreign 40894. 
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 roller on the little 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 & 2 Regent baritone saxophone ( FXH stencil ) / pic 3 & 4 1938 System Menge Copyright / pic 5 1939 FXH cataloque / pic 1 & 2 source eBay.de /
pic 3 & 4 source Cataloque of Copyright Entries / pic 5 source Mönnig Company ( V. Schindler )
fourteenth to sixteenth row: 1939 FXH cataloque source Mönnig Company ( V. Schindler ) / very last picture FXH World Sytem Menge baritone, detailed pictures will follow, after restoration

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