The Mixture and Clarinet on the Great, as well as the originally prepared-for 16' Trumpet on the Pedal, were not installed by Wicks in 1963 (information from Wicks factory documents). They were added at a later time by an unknown builder.
Identified through on-line information from Chad Boorsma -- According to factory documents, the organ was originally shipped from Wicks with 13 ranks, but it appears that the Mixture and Clarinet may have been additions. These stops have a lighter stop tablets than the others. The Great division is entirely exposed on the right side of the chancel, while the Swell division is under expression on the left side of the chancel. Pipes for the pedal are exposed on both sides of the chancel.