The 100 year old statues around Marston Hall, originally the engineering building of Iowa State University, had succumbed to the effects of acid erosion. Each statue represented a field of engineering, and the one holding the spur gear (representing mechanical engineering) was particularly badly eroded with a chipped tooth on the gear
This particular gear repair didn’t require the skills of a gear manufacturing shop but an art conservator.
The article linked here describes the process of restoration and shows a ‘before’ and ‘after’ pic of the rejuvenated mechanical engineering symbol.