Here is the deal on eBay.
I am also disposing of some of my cross use period covers. I believe they are reasonable start prices. The Singapore FDC with Malaya / Malaysia postmarks are harder to find than Malaya / Malaysia FDCs with Singapore postmarks.
To refine, just use “Cross Use”.
For a short history of cross use (these are not for sale): https://myfdc.me/singapore-in-malayamalaysia/
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