Pentax K-1 Review
K-1 II Upgrade
Between May and September, 2018, authorized Pentax service centers offered a paid upgrade service for existing Pentax K-1 owners. K-1 bodies upgraded through this service became identical to K-1 II's purchased new (in terms of specifications). Silver K-1's were eligible for the upgrade, which means that as a result, there are now silver K-1 II's in the wild even though such a model was never produced new at the time.
The only difference between a K-1 II purchased new and a K-1 II upgraded from a K-1 is the camera logo. The latter receives a "II" badge in place of the SR badge, whereas K-1 II's purchased new of course have the K-1 II logo printed on the body itself.
See our Pentax K-1 II review for more details on improvements in the K-1 II.