Here's another neat series from the collection.
From 1925-1929, Germany released a series of semi-postal depicting the coats of arms of various German states/territories. The surcharge went to benefit the Deutsche Nothilfe, a German charity program for which the Reichspost released annual stamp sets from 1924-1935. The stamps were designed by Sigmund von Weech, a German graphic designer who later became famous for his decorative textile designs.
1925

The 1925 series depicts the coats of arms of:
5+5 Pf Prussia
10+10 Pf Bavaria
20+20 Pf Saxony
These issue all have a vertical waffle watermark (Michel wmk 2X).
1926

The 1926 series depicts the coats of arms of:
5+5 Pf Wurttemberg
10+10 Pf Baden
25+25 Pf Thuringen
50+50 Pf Hessen
These issues can all be found with vertical (wmk 2X) or horizontal (wmk 2Y) waffle watermarks, with the exception of MiNr 400 (X only).
1928

5+5 Pf Hamburg
8+7 Pf Mecklenburg-Schwerin
15+15 Pf Oldenburg
25+25 Pf Braunschweig
50+50 Pf Anhalt
These issues can all be found with vertical (wmk 2X) or horizontal (wmk 2Y) waffle watermarks, with the exception of MiNr 429 (Y only).
1929

5+2 Pf Bremen
8+4 Pf Lippe-Detmold
15+5 Pf Lόbeck
25+10 Pf Mecklenburg-Strelitz
50+40 Pf Schaumburg-Lippe
These issues can all be found with horizontal (wmk 2Y) waffle watermarks.
Total quantities produced were:
MiNr 375 -- 4,913,150
MiNr 376 -- 3,926,961
MiNr 377 -- 983,730
MiNr 398 -- 5,268,464
MiNr 399 -- 4,163,636
MiNr 400 -- 438,290
MiNr 401 -- 210,336
MiNr 425 -- 1,207,598
MiNr 426 -- 2,400,716
MiNr 427 -- 2,406,013
MiNr 428 -- 284,850
MiNr 429 -- 156,984
MiNr 430 -- 3,051,237
MiNr 431 -- 4,214,414
MiNr 432 -- 4,898,586
MiNr 433 -- 379,455
MiNr 434 -- 177,788