The small batch of the 10c Rivadavia Browns issued during late 1939 and early 1940 are 1E4s by watermark, but the paper is clearly the CL1A. A comparison with a large selection of the 5c stamp on the same paper from the same era is all that is needed.
![](https://lh3.googleusercontent.com/blogger_img_proxy/AEn0k_tgvyj_zM8Ycu3faeGfVEHTDOeB001gHGJSNTN0c-K9zMFipPXNaVJG3Wrm4K6VZAU6WTRw1TCRFPb83pQgJvuUUp_-Fyl4Vn14tSudg-cbqD5rXpiNxxAsRPfTpqJ2G95e8O4-4FPbv3x3Jx_ZPp9MwnQ355tzOs_nfDVmQj95gU5xwNRraoUJiHq4=s0-d)
I have previously shown this stamp on a June 1939 cover.