I think actually there were some very early P89s that used a different type of magazine...not sure of the serial numbers... chances of getting one of these is nill. actually it could have been a different P... possible the P 94 not the P89...
Same mag -- Important to remember, as very often outfits like CDNN will advertise P89 mags for *less* than P95-marked mags. Don't worry if it doesn't say P95; so long as it says P89, you're good to go!
There are some differentiations in magazines, as Ruger modified the P85/P89 magazines during its production life, for example. To check for magazine compatibility with a specific pistol, simply go to Ruger's website, go to the accessories section, then to magazines, and click on the specific magazines. The description for each magazines covers its compatibility within the overall product line, by serial number sequence when necessary. Ruger's print catalog also has a similar chart in the back of the catalog.
Yes, that is a "first generation" Ruger mag that came out with the P85. The next ones had four holes on the sides, and a metal baseplate. The most current ones have the four holes and plastic baseplate with the Ruger emblem on it.