I have never owned a New Home and probably never will so that buttonholer is excess. The problem was with the configuration of the attaching point. Presser feet and other attachments are not attached to the side of the presser bar, they are attached to the bottom.
I have no machines with that particular configuration and had no way to test the buttonholer before sending it to a buyer. Karma kicked in and what should walk through my door but a New Home Light Running machine!
A lady bought it at a flea market and left it with me to check it out for her.
I had to use the instruction manual to figure out how to thread it.
The machine is in very good condition, all I had to do was clean and oil EXCEPT the New Home Light Running uses the rubber-pulley-against-the-balance-wheel type of drive, not a belt drive. The rubber motor pulley was hardened with age and had pieces chipped out of it and flat spots. The machine sounded like the neighbor's Harley. Miraculously, replacement pulleys are still available and cheap!
I was able to put the machine into smooth-running, quiet operation in no time after receiving the new pulley.
The best part was that now, I have a way to test that buttonholer!
The problem is going to be needles, this machine uses a CC1221 needle considerably shorter than the standard 15x1 and that needle is no longer available. Internet research told me that 206x13 needles can be substituted but the eye is in a different position. I installed a 206x13 and had no problem with the sewing. Further internet research tells me that a better substitute can be obtained by grinding down the shank of a 15x1 needle to make it the same length as the CC1221 needles specified for the New Home. If the owner experiences any problems with the 206x13, I will grind down a few 15x1's for her.
Back to the buttonholer. Before returning the NHLR to its owner, I attached the buttonholer and attempted a buttonhole. Even without the feed dog cover or interfacing, I got an acceptable buttonhole.