The model 26 was in .45 acp, NOT .357. They were made from 1950 until 1966. So, to answer your question, there is no value in something that doesn't exist (a S&W 357 Model 26).
The Smith and Wesson 357 model 686-4 is valued somewhere between $450.00 to $625.00, depending on the condition.
50-550 usd
100-1000 USD
- 50-350 usd
No such model in the S&W line
100-475 or so
50- 500 usd
100-450 USD
100-500 USD
100-400 USD
40-800 usd
100-800 USD or so