This a pair of 1901 501's by Levis® Vintage Clothing - they are exact replica of the 501's that were made & worn in 1901 by US oil prospectors.
This was the first version of these iconic jeans to feature a second back pocket. Loose fitting & with a button fly, these jeans come in 10oz heavyweight non-stretch selvedge denim & with the original silver waist rivet's that were designed to hold the jeans up with braces.
oki-ni recommends you do not use soaps & detergents when you wash your jeans but you won't damage then by doing so. The true denim-connoisseurs way to care for your jeans is to wear them for 4-6 months without washing to allow the caste/colour (patina) to develop. After this, wash in warm water as infrequently as hygienically possible.