To identify the authenticity and value of Guo's paintings and calligraphy works, many factors need to be considered. Here are some suggestions:
1. Understand the author's style and characteristics: Guo's calligraphy works have unique styles and characteristics. Only by understanding his artistic style and characteristics can we determine the authenticity and value of his works.
2. Observe the pen and ink paper of the work: By observing the pen and ink paper of the work, you can judge the age and authenticity of the work. If the paper and ink colors of the works are not consistent with the materials commonly used by Guo, or if the works look like being copied or printed, they need to be carefully identified.
3. Access to relevant materials and documents: Understanding Guo's life, artistic history and works collection, and accessing relevant materials and documents will help to identify the authenticity and value of works.
4. Seek the help of a professional appraisal institution: If you are not sure about the authenticity and value of the work, you can seek the help of a professional appraisal institution. Professional appraisal institutions will have professional appraisers and equipment to accurately appraise and evaluate the works.
In short, the authenticity and value of Guo's paintings and calligraphy works need to be comprehensively considered, including the author's style and characteristics, the pen and ink of the works, relevant materials and documents, and the opinions of professional appraisal institutions. If you are not sure how to identify, it is recommended to seek the help of a professional appraisal institution.