There are three types of seals:

Nintei-hin (認定品) – “Approved item” may be used for all competitions and level tests. Goes through very rigorous testing including but not limited to size, paint durability, quality, etc. (Common usage “Nintei seal”)

Suishō-hin (推奨品) – “Recommended item” color generally matches the Nintei seal of a given manufacturer example: Gentosha = red; Yamagata Koubou = yellow; Goes through the same rigorous testing as the Nintei seal kendama; may be used for testing up through Jun-shodan. (Common usage “Suishō seal”)

Tokubetsu Suishō-hin (特別推奨品) – “Special Recommended item” colors and designs vary, may be used for testing up through Jun-shodan. Does not go through the same rigorous testing as the Nintei seal kendama; generally given for works of art, very high priced kendama, or those of exclusive/limited release. Has the seal but is not often something that is used/played. For the Nintei/Suishō different colors usually mean different manufacturers but that is not always with the Tokubetsu Suishō style of seal. Another example of this
seal is the 40th Anniversary seal released in 2015. (Common usage “Tokubetsu Suishō seal”)
Official Seals
Example:
Ozora ( model name )
Yamagata Koubou ( company name(s) )
Nintei ( certification level )
2008 ( year started )

F16
Mingei Kōeki & Keiyaku Shūryō & Sunray
“Kyōgi-yō” (competition)
1978

Fuji
Hakushinsya
“Nintei”
1980

Sakura
Milkyway
“Nintei”
1984

Fuji & Sakura
Hakushinsya & Milkyway
“Nintei”
1992

Shinfuji
Hakushinsya
“Nintei”
2001

Shinsakura
Milkyway (name change to Art Yoshi 2003)
“Nintei”
2001

TK16 Master
Tamiwa Toy
“Nintei”
2001

Mugen
Iwata Mokkō
“Nintei”
2005

TK16 Junior
Tamiwa Toy
“Suishō”
2007

Ozora
Yamagata Koubou
“Nintei”
2008

Rokuro, Soft Touch
Hakushinsya
“Suishō”
2010

Taiyo
Yamagata Koubou
“Suishō”
2011

Hajimete no Kendama
Gentosha
“Suishō”
2014

40th Anniversary
All Companies
“Tokubetsu Suishō”
2015

Unspecified
All Companies
“Tokubetsu Suishō”
2015.5

Standard
Gentosha
“Suishō”
2016

Unspecified
All Companies
“Tokubetsu Suishō”
2016.12

Pro Racing
Yumu
“Suishō”
2017

Meijin Kiwami
Kashimaya
“Nintei”
2017 (early)

Ozora
Yamagata Koubou
“Nintei” holo
2017

Reshape, etc.
Yamagata Koubou
“Suishō” holo
2017

Stars
Gentosha
“Nintei” holo
2017

Unspecified
Gentosha
“Suishō” holo
2017

Meijin Takumi
Kashimaya
“Nintei” holo
2017

Kodama
Ikeda Kōgyōsha
“Nintei” holo
2017

Pro Racing
Yumu
“Nintei” holo
2017

Unspecified
Yumu
“Suishō” holo
2017
Here is a comparison of two seals that are sometimes confused. The Mugen is on the left and the Meijin Kiwami is on the right.
