Hi Just_fella,
I know of two main references for Ottoman Turkish postmarks.
I use the following books:
Postal Cancellations of the Ottoman Empire by John H. Coles and Howard E. Walker
This was published in four hardback volumes published in 1984-1995.
A more modern alternative is:
Illustrated Ottoman-Turkish Postmarks 1840-1929 by M. Ziya Agaogullari and M. Bülent Papuçcuoglu
I believe this comes in ten paperback volumes.
Both sets are very nicely produced with excellent illustrations.
I've looked at a couple of volumes from the new set but they were too expensive for me.
There were many negative seal postmarks and they are popular to collect.
I'd guess your Hodeidah postmark from Yemen is incomplete just because it was the best available image.
It looks as though it was taken from a torn envelope.
