well a radar is a # that you can read forward and backwards and its the same # like (12344321) just like the word RADAR
it can be considered a double radar, yes. but these types are no where near as valuable as a full 8 digit radar might be. I have a few, and i do keep all that i find, but i dont think i would ever be able to sell them. Also, the better the condition, the better the selling price could be.
Or even better, 23456789, as that seemed to be the most common number used on Specimen Notes from the BEP.