There are many websites about peel-off or tear-off, such as :
http://www.google.com.hk/search?um=1&hl=zh-TW&tbo=d&rlz=1R2ADRA_enHK408&biw=1097&bih=502&tbm=isch&sa=1&q=tear-off+aluminum+seal&oq=tear-off+aluminum+seal&gs_l=img.12...35490.36520.0.38501.4.4.0.0.0.0.94.311.4.4.0...0.0...1c.1.de7gtWBuUBA
But I found only one about push-off, “Combined plastic-aluminum cap (Push-Off cap)” in http://www.emapharma.com/anglais/produits_angl.html