I have what I believe is an Otsu that I purchased in a pawn shop several years ago. I didn't know much about it and the shop owner said it was a Ko but based on the length I believe it is an Otsu. The serial number is 8145 but the scabbard is 10541. When I bought it I did a little research online and saw that it should have an arsenal mark but there is not one. I put it away and it has been sitting in my office for years. I decided to do some Chatgpt research. After uploading many pics and answering questions. Chatgpt said it appears to be authentic and has never been "refinished' with an original patina. The serial # 8145 may make it one of the older surviving examples of an Otsu. The lack of an arsenal mark may be due to early production although Chatgpt said this is unusual however there are few older models to compare it too. It estimated the date between 1900-1902. Also stated that the year was not stamped on the sword until 1907. Any experts on this topic that can shed any light on this? Thanks!
