Peanut Butter Sandwich

Hi everyone, I have a 500 year old katana that I recently purchased in the past 6 months. Unfortunately I had an over zealous guest at my house who was playing with it when I wasn’t looking and evidently held the blade with their bare hands. It seems to have left a stain (which I was aware could happen). Is there a way to remove the stain? I have cleaned it with 100% alcohol and I have re-oiled as normal, but I can still see it. Any advice would be very much appreciated! Thanks, Luke

Hi everyone, This is my first time posting. I was hoping someone might be able to help me. I have recently purchased an old Japanese sword, believed to be around 500 years old (not yet verified). I am keen to display the sword however I live close to the ocean and am weary of salt corrosion. Plus humidity can be high at times as well. Would anyone be able to suggest some sensible ways of displaying the sword with those to factors in mind? I was considering maybe a wooden box with a glass/perspex lid but wasn’t sure if that might cause mould to grow. Links to different display options are welcomed! My second question is about recommendations for preventing the blade from rusting (i.e. waxes or grease). The previous collector I bought the sword off used marine grease. I had heard of Renaissance Wax, but not sure if it is appropriate for my sword. Thanks in advance for your help! Luke