Jig Saw instead of Jigsaw

I have some old puzzles that describe themselves as Jig Saw puzzles instead of Jigsaw.

One I have is a Gold Seal by Whitman. It is in Series No. 622. Its number is 4630 and the name is "After the Rain".

I have searched online, but can't find what time period puzzle makers used the two word description, Jig Saw instead of the one word, Jigsaw like we use now.