Thanks all. I was having trouble visualizing how the linked part would attach.

Can't get to more photos or measurements until tomorrow.

Problem is, I can't 'order' anything. This is my new-to-me, first ever in my life steel road bike, all ready to go except for the minor issue of having no seat. I need to go for a ride ASAP!

Checked one local shop for the hardware tonight and they did not have it, but did have a replacement seat post for $21-- 105% of the cost of the bike!

Will check the other 3 shops tomorrow and if I can't get the hardware locally, will just have to spring for a new post.

Thanks again, will report back on the outcome.