Suddarth has been around for quite a while. I've used them without complaint and have never seen anything negative posted. Mountain Optics is a new incarnation of an older established company. The original owner died and now the name has resurfaced from Idaho to California. Don't know anything about them other than that.
https://suddarthoptical.com/https://mountainoptics.com/If your Nikons are 40 years old, depending on what Nikons you have (kind of like saying I have a Chevy) you are likely going to be better served by upgrading. If those 40 year old are roof prism they came before phase correction, which is a pretty big deal.
