Help IDing a heating mantle

[archivist]

The other day, SWIA visited a very cool surplus warehouse.  There was a giant liquid nitrogen vat, rows upon rows of oscilliscopes piled ceiling high, and even what appeared to be the control panel for a power plant. After hours of digging, SWIA came across the following mysterious heating mantle.  When it is laced up the ends are open and it has one big opening and three small openings. It fits a 500 mL rb flask snugly.  Any ideas what its intended purpose is?  Thanks for any imput.
https://www.thevespiary.org/rhodium/Rhodium/hive/hiveboard/picproxie_docs/000458894-file_i3va.jpg" title="View this image">
https://www.thevespiary.org/rhodium/Rhodium/hive/hiveboard/picproxie_docs/000458894-file_tnvq.jpg" title="View this image">
https://www.thevespiary.org/rhodium/Rhodium/hive/hiveboard/picproxie_docs/000458894-file_j0x6.jpg" title="View this image">

[terbium]

Heating mantle for a resin kettle.

[abolt]

Terb.......................WTF is a "resin kettle"

[methyl_ethyl]

These kettles are used in the manufacture of resinous material.  ie. Dicarboxylic acids could be slowly reacted with glycols in your reaction kettle as the first step in the manufacture of a polyester resin.  The kettles are usually two piece flanged, jacketed, and multinecked for stirring, addition, etc. etc. 

https://www.thevespiary.org/rhodium/Rhodium/hive/hiveboard/picproxie_docs/000458894-file_ihye.gif" title="View this image">

https://www.thevespiary.org/rhodium/Rhodium/hive/hiveboard/picproxie_docs/000458894-file_vqqq.gif" title="View this image">

[abolt]

That looks like a very useful piece of glass.