Caught a dozen HEAD requests for image files from the UA: ICAP-IOD No robots.txt request. All these files are noindexed via X-Robots-Tag (of course the file header would need to be read for the tag to be found.)
ICAP-IOD making requests from Internap: 22.214.171.124 - 126.96.36.199 188.8.131.52/22
Regardless of intent, I blocked them via UA and IP range.
Last June and October I found various HEAD requests from internap , actually a "Private Customer" INAP-SJE-PALOALTOTECHOPS 184.108.40.206 - 220.127.116.11 in this net Internap Network Services Corporation PNAP-SEA-BLOCK4 18.104.22.168 - 22.214.171.124
Not the same UA though, it was "'Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.1; Trident/5.0)'" (yes, with the extra single quote).
And a few more from my big list and some log notes: Internap Network Services Corporation (PNAP) 126.96.36.199 - 188.8.131.52 184.108.40.206/18 INTERNAP-SEA (NET-206-253-192-0-1) 220.127.116.11 - 18.104.22.168 22.214.171.124/19
I see those superfluous quotation marks now and then. (Query: Does there exist any legitimate UA that either begins or ends with a quotation mark?) It now occurs to me to wonder if the originator is copy-and-pasting from some standard UA list, and accidentally included the enclosing quotes.