I'm sure I saw this image described as an artwork rather than an emulsion photograph (unless that was an artist's impression of an originating photograph).
Is that a 1917 copyright logoform "SFC"? Admittedly that could've been penned-in to a production negative during wet processing, and some old pictures do have hallmarks like this. But it's also consistent with a 2D art piece, done using india ink/charcoal/chalks, in a slghtly pointalist style.
Teratogenic/semi-chimeric twins: would this morphology be biologically feasible, as depicted here?
I can see how a peri-fœtal inter-cranial bond could occur (as per the Two-Headed Boy of Bengal) with the resultant mutual inversion, but how could the two fœtuses occur, co-orthoskeletally, and there be a viable human living to middle age or later? Put another way- surely there would be an under-developed skeleton (tiny spine/limbs etc) extending into and between the brain hemispheres of it's host? Also, how would there be sufficient vascularisation to support even a non-animated parasitic head, upon a host head? Shared neck, Zaphod style, yes. But I question the long-term viability of this duplex existence.