I went through Sana'a in the 70's and found the locals friendly, especially in the market where one did some shopping - they wanted my trade!
Apart from admiring the architecture, whilst there I picked up a some Maria Theresa Thalers. ISTR that at the time Thalers were legal tender in Yemen and in the market enterprising stall-holders had silver-soldered bits of cut off coiled-spring curtain track (as used to hang curtains on kitchen doors) to the top of the Thaler as a loop through which to thread a neck chain.
The one shown in my photo makes a chunky necklace which my wife wears occasionally.
Thalers bearing the date 1780 are not worth much, too many were made including many made by the London Mint.
As I mentioned elsewhere Maria Theresa thalers bearing the date 1780 are a "protected coin" for the purposes of Part II of the UK's Forgery and Counterfeiting Act 1981. This Act makes counterfeiting legal as long as it's done by the government!