Hi Michael,
I hope by your reply that you think my assignment as the rear tubes is correct!(the caption is forward)

The following image is I believe of the forward tubes of U 135, I love the use of a cut-down gate legged table as a work bench.

[www.greatwarin3d.org]

Would you be happy to agree that these other interior photos are most likely to be U135 as well?

[www.greatwarin3d.org]

[www.greatwarin3d.org]

[www.greatwarin3d.org]

And in this last internal photo showing switchgear - is this where the batteries lived as well?

[www.greatwarin3d.org]

Sorry, lots of questions but there are virtually no internal drawings of WW1 subs.

Thank you
Paul