Some sleuthing was needed to determine when it was made. First pointer is that Manson had all of his tats before Ginger Fish joined the band in March 1995.
And I remembered Manson removed his lip-ring permanently one night after being arrested. Find out when that was and you can narrow the dates down. In the photo above, you can see the lip-ring, it's a 'pre-16-hours-in-jail' picture.
Manson was arrested 27 December 1994 on a charge of 'violation of the Adult Entertainment Code' - public nudity - after a set at Jacksonville's Club 5. If he removed his lip-ring that night then he had the Uncle Creepy tat before then.
Also, there's no Uncle Creepy tat at the Slammie Awards on 3rd July 1994, which means it was made between 3 July and 27 December 1994. Am I pedantic or what.
Update: Then, going by this old candid photo, I realized he had the tat by September 1994.