A Couple Of Unknown Chinese Stamps

After organizing my Chinese stamps collection I am left with a couple of stamps I have been unable to ID. An few of them probably will be revenue stamps I guess.
Any help appreciated!

Second row. First stamp.

Rep of China.

1948

Postage due.



Second row. Second stamp.

PRC

1950.

East China issue with overprint.

Second row. Third stamp.

Rep of China.

1947.

Sun Yat-Sen Masoluem.


First row. Second, third, fourth stamps.

Rep of China.

Review Scott entries starting in 1938.

Top row. First stamp.

Rep of China.

1947.

Rural mail delivery.

Top row. Second stamp.

Scott. 1940 series.



Top row. Third stamp.

Scott 1938.

Believe base stamp is #346.

However, Scott indicates imperforates of this series were "not regularly issued".

Thanks very much Calstamp!
Some of these stamps I should have found myself in hindsight.
But I guess I became a little stamp blind after going through the catalog for the 10th time. :)

The imporferated stamp is in my Scott (Scott Classic stamps) mentioned as printers waste.

I still am unable to find the second and the fourth stamp in the first row, I fear these are not listed in my catalogs. (Scott until 1940ies and Michel China)

Northwinds, try the Sun Yat Sen series of 1931

Peter

@Peter

Thanks for your post. Why would you refer to the 1931 issue? Its a different design.
Perhaps I am overlooking what you meant?

I have gone through my catalog many times but the 50 on 5 green surcharge I am unable to find.

Peter

Northwinds...

Plz check the perforations on your stamp. Is it 12.5?

If so, plz take a look at (Scott catalogue) Shanghai amd Nanking.

9N9 (#352).