“What kind of robbery is not dangerous?”/“A safe robbery.”

A robbery riddle is:
 
Q: What kind of robbery is not dangerous?
A: A safe robbery.
 
The riddle has been cited in print since at least 1869.
 
           
1 September 1869, Daily Eastern Argus (Portland, ME), pg. 4, col. 1:
What kind of robbery is not dangerous? A safe robbery, of course.
 
Chronicling America
27 May 1870, State Rights Democrat (Albany, OR), “Chips,” pg. 1, col. 7:
What kind of robbery is not dangerous? A safe robbery, of course.
     
Google Books
29 May 1875, Harper’s Weekly (New York, NY), pg. 442, col. 3:
What kind of robbery is not dangerous?—A safe robbery, of course.
 
Google Books
Biggest Riddle Book in the World
By Joseph Rosenbloom
Illustrations by Joyce Behr
New York, NY: Sterling Publishing Company, Inc.
1976
Pg. 170:
What kind of robbery is not dangerous?
A safe robbery.
   
Google Books
Riddles with a Reason:
Improving language skills through wordplay
By Jeri S. Cipriano
Torrance, CA: Good Apple
1998
Pg. 10:
What kind of robbery is not dangerous?
Answer: A safe robbery.
 
Google Groups: alt.religion.rabbet
Humor from the Net
Bill McCray
8/30/03
PUNS OF THE WEAK for the week ending August 23, 2002, part 4
(...)
What kind of robbery is not dangerous?
A safe robbery.  (Connie, 12)
 
Twitter
The Daily Funny‏
@_thedailyfunny
What kind of robbery is not dangerous? A safe robbery.
10:39 PM - 9 Oct 2009
 
Twitter
Lucky Score‏
@LuckyScoreNet
What kind of robbery is not dangerous?
A
safe robbery.
#Joke from #CriminalJokes in #Jokes, #Humor and #Satire
7:55 PM - 11 Nov 2017