<p>This is a small glass plate negative (c. 7cm x 4cm) captioned on the containing wallet as "Felix Man. Munich Beer Cellar".  No further provenance so no verification of that is possible.  The negative is deeply tobacco coloured, giving this blueish colour when inverted.
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The chap at the table on the left appears to have some sort of shaven/mohican look.  Unsure of date, but estimated 1930s?
<a rel="nofollow" class="external text" href="https://www.flickr.com/people/24469639@N00">whatsthatpicture</a> from Hanwell, London, UK
CC BY 2.0
<a rel="nofollow" class="external text" href="https://www.flickr.com/photos/whatsthatpicture/4977221391/">Munich Beer Cellar, attributed to Felix Man</a>