This should be an easy typeface to identify but I haven't come up with an exact match yet.
This was used in the 70's for the titles on some paperback books published by New English Library. The closest I've been able to come is Century 725 Black by Bitstream.
With only the small three letter sample (I couldn't find any other samples of the same face) it's been a bit difficult using the type identification tools available on the web.
The things that make this not quite Century 725 Black are the arm in the center of the F having a bit less vertical flair in the serif and the thin stroke on the X passing through as one continuous line instead of being offset on the left and right. Also the serifs in the sample appear to be a bit thicker.
Thanks for any help.