Keuffel and Esser Co Paragon transit

purchased a Keuffel & Esser Co transit that seems to date from 1958. I have attached pictures - I had to wipe out some watermarks from the person I bought it from ( I haven't received it yet) so that's what the blurs are on the photographs. The model number is N5130 and then it says "with 5097-70" under that. The S/N is 156907, which is where I got the date from. I haven't been able to find this particular model number NOR what the 5097-70 means. However, there is another 1958 transit here:

http://www.technicalcollectibles.com/Antique_Surveying_Instrument.htm

on sale for $1000.00, which looks exactly like the one I have.

Thanks,
Pat

Good