Get the spatial reference identifier

SRID(stbox): integer

SELECT SRID(stbox 'STBOX ZT((1.0, 2.0, 3.0, 2000-01-01), (4.0, 5.0, 6.0, 2000-01-02))');
-- 0
SELECT SRID(stbox 'SRID=5676;STBOX T((1.0, 2.0, 2000-01-01), (4.0, 5.0, 2000-01-02))');
-- 5676
SELECT SRID(geodstbox 'GEODSTBOX T((, , 2000-01-01), (, , 2000-01-02))');
-- 4326

Set the spatial reference identifier

setSRID(stbox): stbox

SELECT setSRID(stbox 'STBOX ZT((1.0, 2.0, 3.0, 2000-01-01),
  (4.0, 5.0, 6.0, 2000-01-02))', 5676);
-- "SRID=5676;STBOX ZT((1,2,3,2000-01-01),(4,5,6,2000-01-02))"

Transform to a different spatial reference

transform(stbox,integer): stbox

SELECT transform(stbox 'SRID=4326;STBOX T((2.340088, 49.400250, 2000-01-01),
  (6.575317, 51.553167, 2000-01-02))', 3812);
-- "SRID=3812;STBOX T((502773.429980817,511805.120401577,2000-01-01),
  (803028.908264815,751590.742628986,2000-01-02))"