Good call, bigehrl !!
Lost In Space has another mistery: the decal set has 2 decals for Insert balls: Insert 4 balls and Insert 5 balls. Since this machine works with 4 balls, whay did they put the 5 balls decal on the set?
You can see both decals here:
http://www.marcospecialties.com/control/keywordsearch;jsessionid=FF17931DABA3F211B9E56975D3E1AC40.jvm1?SEARCH_STRING=lost+space+decal