. ▁ ▁Vari ety ▁in ▁the ▁shapes ▁is ▁achieved ▁by ▁use ▁of ▁con ca ve , ▁convex , ▁per for ated , ▁non - per for ated ▁and ▁be aten ▁patterns . ▁ ▁The ▁spir al ▁st air case ▁turns ▁ 3 6 0 ▁degrees ▁in ▁a ▁height ▁of ▁. ▁ ▁It ▁is ▁constructed ▁of ▁ter raz zo - filled ▁steel ▁t read ▁p ans ▁carried ▁off ▁two ▁bra cket ▁supported ▁struct ural ▁steel ▁carriage ▁pieces . ▁ ▁Mod ifications ▁and ▁dates ▁▁ ▁late ▁ 1 9 5 9 ▁- ▁construction ▁comm enced ▁▁ 1 9 6 0 ▁- ▁construction ▁completed ▁▁ 1 9 6 5 ▁- ▁re location ▁and ▁installation ▁of ▁P AB X ▁room ▁to ▁fifth ▁floor ▁▁ 1 9 6 7 ▁- ▁partition ing ▁to ▁second ▁and ▁third ▁flo ors ▁▁ 1 9 6 9 ▁- ▁partition ing ▁to ▁the ▁ground ▁and ▁me zz an ine ▁▁ 1 9 7 0 ▁- ▁partition ing ▁from ▁the ▁mez an ine , ▁first ▁to ▁third ▁flo ors ▁▁ 1 9 8 1 ▁- ▁partition ing ▁to ▁the ▁first ▁floor ▁▁ 1 9 8 4 ▁- ▁conversion ▁of ▁fourth ▁floor ▁Care t akers ▁flat ▁to ▁office ▁space ▁and ▁partition ing ▁ ▁Heritage ▁listing ▁ ▁Lin er ▁House ▁is ▁associated ▁with ▁the ▁Wil h . ▁Wilhelm son ▁Agency ▁and ▁the ▁historic ▁use ▁of ▁Bridge ▁Street ▁as ▁the ▁hub ▁of ▁offices / agen cies ▁associated ▁with ▁sh ipping . ▁ ▁It ▁was ▁constructed ▁at ▁the ▁close ▁of ▁the ▁ 1 9 5 0 s ▁-