Qianlong polychrome plate marked

[hoogenbosch67]

I am not sure about the mark Qianlong or later Yongzheng

[hoogenbosch67]

bottom and mark

[peterp]

The mark is too small. It seems to be a Jiaqing mark.
The decoration is late Qing, so I would think about Jiaqing-Daoguang. Basically I tend to think it is more likely to Daoguang (that could also have a Jiaqing mark), due to the decoration, especially the bats.

Foot rim shape and the bats painted underneath the rim can only be from the late Qing dynasty.