Hi Good Morning,
Does anyone have experience of a dual sim card holder for use with a standard Nokia Mobile and as to whether they actually work in a satisfactory manner.
I am aware that one can buy a dual sim card phone but the choice is very limited with products mainly from China.
Thanks so much.

Years ago I bought a triple SIM card holder to run on my old Nokia 6310i. I found an outfit on the web and ordered online and it was less than GBP10 IIRC. (I have checked and I had bookmarked their site but it doesn't seem to open now!).
It fitted between the battery and the phone, and had a little switch on the back which changed the SIM card you chose to use. Obviously it only worked one SIM card at a time.
The downsides were it made the 'phone a little bulkier, and you had to turn the 'phone off before you could select another SIM card, but hey, it was easier than running around with three mobile 'phones!

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I ran dual sim card holder in which each sim card was cut down to size (from a provided template) and inserted into a carrier that was the same size as the original card. Switching between sims was a software selection, they couldn't both run at the same time. Also included in the pack was a blank to insert one of the cut down cards to run the phone off one card. The carrier was thin aluminium and very slightly thicker than the original card ( cigarette paper thicker.) That extra thickness, in my phone, led to deeper than design tolerances indentations in the sim contacts and eventual failure of one of the cards. It could have been my fault for repeatedly extracting the carrier to show it off!
Most if not all modern phones will have the software to run 2 chips.

Even some of the older ones. I ran a Nokia 3410 for a couple of years with dual-sim; changed sim with a Nokia hash-code (can't remember it) when going into areas of UK where my own provider's coverage was patchy. Never a problem.