I'm looking for the death year for Marion Wiles Keller. He was born in
1905 and received his PhD from Indiana University in mathematics in
1932. He spent his life as a working mathematician.

Hello Mbhenry,


Marion Wiles Keller died March 29, 1993.

Here is the record  from the FamilySearch International Genealogical Index

Marion Wiles Keller  
Male     
    
Event(s): 
Birth:  21 JUN 1905   Dayton, Montgomery, Ohio 
Death:  29 MAR 1993    
 
Parents: 
  Father:  John Barney Keller  
  Mother:  Corinna B. Wiles     

Source:  
FamilySearch International Genealogical Index
http://www.familysearch.org/Eng/Search/IGI/individual_record.asp?recid=100094465148&lds=1&region=11&regionfriendly=North+America&frompage=99




Search criteria:
FamilySearch International Genealogical Index


I hope this helps!  If anything is unclear with my answer, please ask
for clarification.

Best regards,
Bobbie7

Excellent work. Many thanks bobbie7.