Rochester specializes in obsolete or hard to find semiconductors, but they source their stock from genuine, authorized sources, hold on to these parts, and charge you a premium for the privilege of being able to buy obsolete or discontinued parts. As far as I can tell, they source their stock from authorized manufacturers or distributors, so it is practically impossible for them to have counterfeit or mishandled stock. As you report, ADI confirms this, so I would trust them the same as any 'new stock' distributor.
The price penalty you end up paying might be painful for hobbyists or 'little folks' like us, but they will have the genuine article.
A point to keep in mind is that a number of semiconductors become obsolete simply because of the packaging becoming obsolete. These days, anything 'through-hole' is disappearing, but the same die might still be available new in a different package. So, if you could buy a new chip, perhaps in an SMT package, and then mount it on an adapter board, you can get genuine parts that can work in a device that needs an obsolete package.
To make that simple, TI sells a really nice evaluation module for a very nice price - it's a package of 5 different SMT to DIP adapter PCBs that are well built and very nicely priced. Search for 'DIP-ADAPTER-EVM' and you will find it on TI's site, as well as Arrow, Mouser, Digikey and others. This kit gives you five each of five different SMT op amp package adapters, that convert the SMT pinouts to a simple 8 pin DIP footprint. You have to solder it up yourself, but it's not so hard, and this allows you to use modern chips in an 'old style' 0.1" 8 pin DIP layout.
Not to beat a dead horse, but buying ICs from non-authorized sources is usually a huge waste of time, unless you have some way to verify that the devices are genuine, and also that they have been handled properly. For me, a modern part on an adapter board is a good way to be able to use a genuine part in an 'obsolete' application.
The price penalty you end up paying might be painful for hobbyists or 'little folks' like us, but they will have the genuine article.
A point to keep in mind is that a number of semiconductors become obsolete simply because of the packaging becoming obsolete. These days, anything 'through-hole' is disappearing, but the same die might still be available new in a different package. So, if you could buy a new chip, perhaps in an SMT package, and then mount it on an adapter board, you can get genuine parts that can work in a device that needs an obsolete package.
To make that simple, TI sells a really nice evaluation module for a very nice price - it's a package of 5 different SMT to DIP adapter PCBs that are well built and very nicely priced. Search for 'DIP-ADAPTER-EVM' and you will find it on TI's site, as well as Arrow, Mouser, Digikey and others. This kit gives you five each of five different SMT op amp package adapters, that convert the SMT pinouts to a simple 8 pin DIP footprint. You have to solder it up yourself, but it's not so hard, and this allows you to use modern chips in an 'old style' 0.1" 8 pin DIP layout.
Not to beat a dead horse, but buying ICs from non-authorized sources is usually a huge waste of time, unless you have some way to verify that the devices are genuine, and also that they have been handled properly. For me, a modern part on an adapter board is a good way to be able to use a genuine part in an 'obsolete' application.