Didn't he appear in another role on the series as well?
Yes, he was a recast as Lt. Riley in the Laura storyline. Here's his capture/caption for the Robs slideshow for January 18th :
(http://www.dsboards.com/eventimages/0118ds_0.jpg)
1967: Ep #148 - Lt. Riley (poor Vince O'Brien - always a
recast - never an original) reveals a witness says that,
contrary to Laura's claim that she left Phoenix five days
before the fire, she saw Laura on the day of the fire.
As for how often he appeared as Sheriff Patterson, I think it was more than 2 or 3 times - but it might be less than 10. Our minds tend to play tricks. Just look at how often it seems that Mrs. Johnson appears - yet she was only in 56 eps. [ghost_wink]
Here's the scene (from Ep #174):
(http://www.dsboards.com/images/0174-31.jpg)
(http://www.dsboards.com/images/0174-40.jpg)
And for those who've never seen that ep, yes, that is John "Gladstone" Harkins as Lt. Costa. [ghost_smiley]