I know it's an old thread, but here's some information that might be useful for the fellow forumers.
This M6306 chip is actually the discontinued OKI MSM6306 3 3/4 DMM IC, used on several Yokogawa digital multimeters such as Model 7534-03 and also on some units rebranded as HP (E2378A and E2377A) and Soar (3255).
Samsung released the KAD7001, a MSM6306 clone, supposed to be a direct replacement, but there are rumors that a few pins are numbered differently.
Other than that, all the rest still exactly the same and it's datasheet could be a very useful resource for repairing some of these nice multimeters.
Here's the Samsung KAD7001 datasheet for download:
https://cdn.datasheetspdf.com/pdf-down/K/A/D/KAD7001-Samsung.pdf