Drain and manhole covers of TBS

The drain and manhole covers of the TBS company are ubiquitous in the Netherlands. You can recognise them easily by their triangular logo. The covers often display the patent number 53348, which is a special construction of drains linking the cast iron and concrete.
The TBS company was founded in the 1930s by O. Zimmerman. TBS stands for Technisch Bureau voor gietijzer producten Soest (Technical Bureau for cast iron products Soest (a town in the Netherlands)). Now it is the market leader in the Netherlands.
Website: www.tbs.nl