All the filters listed in this article may contain asbestos and/or chromium. It is not inherently dangerous to use them but it’s at your own risk.
And no, the GP-5 was not used by the military
The East German NVA and other government organizations all got gas masks issued. In case of a nuclear war everyone needed to carry one.
The full list of masks used includes:
ShM-41/M/MU & foreign copies
MM-1
ShMS
PRVU
PBF
M10M
Timeline
1950’s
During the 1950’s the following gas masks were newly issued for service
ShM-41
ShM-41M
ShM-41MU
MM-1 for soldiers to use radio or optical equipment with, such as tank visors or binoculars
Few others that were used in small amounts are the Czech M52,
Czech M52U, Polish SzM-41, Polish SzM-41M, Bulgarian BSS-MO-4U
Filters
Medi ÜB
BSS-MO-4U
EO-16
EO-65-K
PLACEHOLDER – PICTURE WILL COME HERE
1960’s
In the 1960’s one new mask was introduced for service
ShMS for troops that needed to use optical equipment
1970’s
In the 1970’s two new gas masks were introduced for service in the NVA.
PRVU for rocket troops
PBF for riot police and other organizations that needed a lightweight mobile mask such as the Grenztruppen
Filters
DP-1 for use with the PRVU
EO-19 for use with the PBF
1980’s
In the 1980s one new mask was introduced.
M10M first introduced for the Grenztruppen but later for general use with the introduction of UTV
Filters
LF-10 for use with the M10M
Newly introduced rubber carrier with plastic toggle 
Newly introduced PBF gas mask carrier 
M10M gas mask carrier, it was similar to the standard one but had less pockets 
UTV gas mask carrier setup
International Militaria 