Japan - Revenue Or Other?

Found these in a small collection of Japanese stamps and cannot find any information on what they may have been used for? Any insights would be helpful.

The left one looks like a registration label.
The right one does as well, but might be an express label.

They are both registered labels, used during the Showa era.

The only reliable reference for these labels is the "Standard Catalogue of Japanese Revenue Stamps", 2010 edition by Shimomura.

The left one (with "TOKYO") is for foreign registered mail, and judging from the font and their alignments, it is very likely to be #CA10 (used from around June 1950) or #CA11 (used from around April 1953).

The right one is for domestic registered mail, and is one of the "horizontal type", Type 2, used from around 1933 to 1957. There are so many varieties and therefore very difficult to identify, but this one (with serifed "2") seems to be not listed in Shimomura catalogue.

Hope this helps !

- Hironobu

NSK and unechan thank you both so much for your valued information. Very helpful.