Hi. I am not an expert on these but I believe this is a Francotyp type of meter that was introduced in 1924. I am not sure how long this metered impression was used but I think it was well into the 1930s. Your cover has wide spacing between the dater hub and the 'value' portion. Some of these are known to be much closer together.
The airmail 'etiquette' is common and seen on many covers. I have seen the red sticker before but I am not sure how or why it was used for.
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