I'm currently working on a couple of projects that would require a telephone style handset, and I've always liked the rugged and almost techno-punk look of the military H-250 handset.

So, instead of try to source one off eBay (and having to deal with the 1000 ohm speaker and dynamic noise-cancelling microphone), I decided to design up and 3D print a version that I can customise to suit my needs. I've posted the parametric OpenSCAD file here, so you can edit it to use whatever microphone and speaker elements you choose (although I'll post a link to the parts I've used), as well as whatever cable diameter you want. 

I've uploaded STL files for the individual parts, as well as a plate so all parts can be printed in one go. I ran into some problems with bed adhesion, so I've also added a version that allows you to use a brim, without having to remove the brim from all of the internal cutouts where it isn't really needed. There are two ways of assembling the handset, either using M3x6mm countersunk self-tapping plastic screws, or alternately gluing the two halves together, with short lengths of 1.75mm filament used as alignment pins. The STL files for all of these variants are uploaded here.

I've marked this as a complete project, and while I would like to add a push-button, I don't have plans for this at this stage

* Image credit to Tennessee National Guard, CC-BY-2.0,  https://commons.wikimedia.org/wiki/File:Tennessee_National_Guard_communications_specialist_trains_at_Georgia%27s_RTI_(5393754639).jpg (... with apologies for the lame joke)