I did a quick check of the data sheets for the DS3695N/NOPB, the SN75176BP and the MAX485CPA+ chips on the Mouser site and they all appear to be "RS-422/RS-485 Interface IC" chips with the same pinouts. The manufacturers just are using their own part numbering. I use the SN75176 but I've also used the MAX485 parts in the past and both work just fine.
Before you order make sure you're ordering the correct 'package'. Most units of that vintage had 8 pin IC sockets for 'thru-hole' parts (rather than the newer surface mount chips) that let you insert/replace the chip without needing to de-solder/solder anything.
Feel free to e-mail if you think I can be of further assistance (I've been neglecting visiting Control Booth lately).