I'm thinking that the receipt is for something else because the price is listed as a "vacuum cleaner accessory". Maybe she sent for some bags or something & it's a mail order receipt.
And besides, that's not a 1967 Singer buttonholer. I would date that buttonholer closer to the late 40's thru the 50's. I have a buttonholer that was my mom's, bought in the mid-late 60's at the Singer shop that used to be in town...it was in the red, white, & green cardboard box & it's plastic with plastic cams. It has a $14.95 price sticker on the box. If that buttonholer was bought in '67, it may have been used.