Formally silver kanji were introduced on December 28, 1937 by Ministry of Finance Ordinance No. 60 that prohibited the use (as wartime austerity measure) of gold in inscriptions, trademarks, etc.
Excerpt from original ordinance.
"... may no longer be produced ...
4. Gold letters, gold silk...
datingjapanese award
datingjapanesemedalcasedatingjapanesemedals
datingjapanese orders
gold kanji lettering on the japanese order cases
golden vs. silver kanji on case lid
japanese awards and decorations
japanesemedalcasejapanesemedalcase with golden inscription
japanesemedalcase with silver inscription
japanese order case with silver inscription
japanese order case with silver lettering
silver kanji lettering on japanese order case
time borders of silver kanjies