I'm likely more picky as I collect other technological artifacts. If it came from the unitron factory as a 142, then it's an "original 142", if it was put togather from parts, then it's not an original 142 but as long as all the parts are from 142's it's a "restored 142". the key concept is: is it exactly as it came from the Factory?
if the tube was cut shorter and a non unitron objective put in, it's not a Unitron 142 any more. Its an f11 telescope made from Unitron parts.
Also, unless Unitron specifially sold Unitron kits intended for you to you assemble yourself, if you made it yourself from unrelated new old stock or used spare parts from scratch, then you have an obligation to disclose that to any buyers.
a made from parts scope is most definitely not an original 142 as it never came as is from the factory. It is however, an Authentic 142 paradoxical as that may seem.
An Original is that from which a copy, reproduction, or translation is made according to Merrim-Webster.
None of this answers whether its a classic telescope or not. Classic is a little more fluid a concept.
The word classic generally means something that is a perfect example of a particular style, something of lasting worth or with a timeless quality. So yes indeed, your telescope is a classic telescope: it's a classic f11 refractor in the style of a Unitron. Classic cars have a particular style of lasting worth and timeless quality indeed.
People confuse Classic with Vintage or antique. They are not the same.
The handful of pennies in your pocket are all classic pennys. They may or may not be vintage pennys depending on how old they are. But if you made them yourself, they are not original pennys, they are conterfit pennies. It dosent matter that you made it from the same parts the Treasury did. It didnt come from the treasury as a Penny.
You have an awesome telescope, I like it a lot. its worth a good chunk of change. Nothing unworthy or less valuable about it. Enjoy it and use it and dont worry so much about labels and what anyone else thinks. It's a classic telescope.