What lies beneath?

Secretes of Rembetes  1933 in Karaiskaki, Piraeus!

A very interesting conversation  in Rebetiko Forum regarding the etymology of the word Rebetiko and Rebetis, gave me a reason to research on the internet , old and famous photographs of Rebetes.

One of the most famous one, is the 1933 photograph taken in Karaiskaki Piraeus. At the left, holding a bouzouki is Markos Vamvakaris, and in the middle with a guitar is Yiorgos Batis.

Accordingly to Wikipedia, the photograph is been scanned from the book  "Fünf Griechen in der Hölle", ("Five Greeks in Hell") Trikont LC 4270 (1982). ( * )

Trying to sharpen the image, looking  for more information, I noticed at the bottom center of the photograph, a dark stain.   

On a closer look, the dark stain, didn't look like a stain after all.

I reversed horizontally the image, and surprisingly I discovered that the original image when first scanned (assumption 1) , kept some traces of information which had been written at the back side.

Was it a hand writing from the owner of the photograph? Maybe a postcard photo with wishes from the sender to the recipient? Was it a stamp from the original photographer? Was it a later in time note from the back page of the book ? (assumption 2)

I passed the photograph through special filter in an attempt to figure out what was written at the reverse side.

But the traces from the text written at the back side of the photograph were too weak, to help me come to a solid conclusion.

Making a risky assumption (assumption 3) I would say that the note at the back side of the photograph looks like a hand writing in Greek language. But this last conclusion is being  based totally in  3 assumptions, and some small traces of a multiple times scanned photograph, dating 80 years old.

If anyone, has more information regarding what lies beneath of this unique 1933 photograph, please email me at spyrosdimis@yahoo.com Thank you!

Updates:

( * ) Accordingly to the researcher and author Nikos Politis, the photograph is been scanned from an LP music album with two vinyl records.

The album published in Munich in 1982 with title  "Fünf Griechen in der Hölle", ("Five Greeks in Hell"-Πέντε Έλληνες  στον Άδη ).

( ** ) Accordingly to the researcher and author Stavros Kourousis, the original photograph is being kept at Gennadius Library (http://www.ascsa.edu.gr/index.php/gennadius/)