it's a paint scraper!
linked example
I used this to scrape paint in my basement. The triangle blade was great for walls, I used the rounded one to remove window glazing.
https://www.amazon.com/dp/B000BQWPOM/ref=cm_sw_r_cp_api_glt_i_ZX24FQ18Y8RZWJ2MBP5S?_encoding=UTF8&psc=1