This is one of three known postmarks for Gayah which was in use between 1886 and 1897. This datesstamp was apparently lost during the destruction of Gayah by Mat Salleh in June 1897.
Does not show up very well. There is a faint G and A at the top. That is why I have not noticed it until today. Had it for years. A red Gayah postmark on SG1 should be a dream but unfortunately it is not a vivid dream.
Update Well, things are looking up here!. With a better resolution scan, I think we have a very rare red prefix "A" rather than the more common prefix "B" stamp. The date reads like A 15 FE 1886. Also the day and month are transposed.