Here is a reference for the topic: the 2nd ref. has more details
Kolahi, J., Bang, H., & Park, J. (2009). Towards a proposal for assessment of blinding success in clinical trials: up-to-date review. Community dentistry and oral epidemiology, 37(6), 477–484. https://doi.org/10.1111/j.1600-0528.2009.00494.x