OK Pommie here we go,
The first pic you posted in Japanese is basically a service warning. Before replacing parts in this unit make sure that it is unplugged.
The second is a cabinet inspection stamp. Showa 54 is the 54th year of the Showa era which means that this CABINET was last inspected in 1979 before it left the factory. It could not have left the factory as Gyruss as Gyruss was released in 1983.
The third indeed does refer back to the first pic you posted, however this is also telling the tech to make sure the power is connected after the switch settings have been applied (maybe dip-switch settings?)
The forth picture top sticker refers as Malenko says to this unit being for indoor use only, the second sticker is marking a main ground connection.
The Konami sticker is a little of a mystery. Konami entered the video game business in early 1979. This being said with the inspection sticker being from 1979 the only game this cabinet could have contained when it shipped from the factory would have been a game called Space Wars. A link to screen shots and cabinet shots is below.
http://www.konami.co.jp/ja/corporate/history/product.htmlI also found a little better pic of an original Konami Space War cabinet.
Don't be futzed about the control panel being different. I don't think that the control panel you have there is an original Space War controller. I think that the controller you have is from a Japanese Space Invaders machine Many of the original cocktail cabinets here in Japan were Frankensteined in order to fit games from other manufacturers here in Japan. It's really sad. Arcade machines here in Japan also started as upright stand up cabinets but soon went to sit-down cocktails and finally the Candy Cabs and Viewlix you see today. It is virtually impossible to find an original stand up Arcade Cabinet here in Japan.
Anyway, I hope the info helps. I can't tell you if the PCB is a Japanese Gyruss with out more pics. If there is any writing in Japanese at all on the PCB I think that I may be able to help you.
Jigenjuke
Anyway here is another pic.