Welz tango

The Welz tango resembles Loetz and Kralik tango but if you look closely they have no pontil mark and the rim is fire polished. I have no idea how they were made with such consistency. They are sometimes signed with a faint acid mark "Made in Czechoslovakia". There is a very similar type (I am looking into them) that has a variegated rim...they may or may not be related. the fourth picture shows a nice color range between the lemon yellow and the blood red. The green is a very rare color and helps to identify other shapes.

any new color pics are most welcome.