The Bulgarian National Bank knows only one type of 1, 2 and 10 stotinki coins from 1999 (Cu-Ni-Al) and one from 2000 (Steel+Bronze), plus one proof set from 2002 with "CuNiZn coins" (that's the 10 to 50 stotinki).
circulation: http://www.bnb.bg/NotesAndCoins/NACCoinsCurrency/index.htm
proof set: http://www.bnb.bg/NotesAndCoins/NACCommemorative/NACCommemorativeEmissions/index.htm
In the coin sheets we have the CuNiAl coins also with 2000, is this a mistake? And both coin types are listed as 2002 proof variant?
https://en.numista.com/catalogue/pieces5366.html
https://en.numista.com/catalogue/pieces28610.html
https://en.numista.com/catalogue/pieces5367.html
https://en.numista.com/catalogue/pieces28608.html
https://en.numista.com/catalogue/pieces1982.html
https://en.numista.com/catalogue/pieces28611.html
Also, the mintage figures don't seem to be correct. Here (pg 5) they mention 550 million pieces of 1 stotinka in circulation. And (last page) they took out of circulation 39 mn pieces in Jan-Mar 2015. I figure the Bulgarian coins are still minted with the year 2000.