Did you know that LinkedIn has over 42K members who list MBA as part of their last name? It also has over 20K people listing CPA as part of the last name, over 30K PHR's, 22K+ SPHR's, thousands of PhD's (or Ph.D's), etc.
For this search to be of any use, you will, of course, need to add your target keywords, companies, or locations, to narrow it down.
While you will be missing some SPHR's using a search like this, here's what is very special about these searches.
1) You will see all the search results, no matter what type of LinkedIn account you might have. This is actually true for any type of LinkedIn people search, so it's not that special. Somehow there's a perception that paid LinkedIn accounts or special paid accounts like LinkedIn Recruiter find more search results. They don't.
2) Here's what is really special. You will see all the last names, no matter whether these people are your third level connections, or inside or outside your network, or outside everyone's networks.
You will, in fact, see more than just the last names. Compare this search result, that is outside of the network...
...and its profile viewed from a basic account...
...with the very same profile in the search results, from the very same account, if you use the PhD keyword:
... and here's what it looks like now:
Of course, Google (that has no account on LinkedIn) can see the same information in the public profile:
But the info that we could see in the unnamed, out-of-network profile in the LinkedIn search results is only: the location, the job title, and the industry - and in many cases it's just too little for X-Raying on Google. (In the good old days LinkedIn used to show more for out-of-network results.)
Conclusion: use a degree or a certification abbreviation in the last name field, and not only uncover the last names, but also public profiles' links and much more information for every search result, no matter what your account is.
Since all (free and paid) LinkedIn personal accounts hide the out-of-network names in search results, this gives everyone the power of LinkedIn Recruiter from the convenience of a personal account for this special type of search.
I'd be glad to connect on LinkedIn.