The existence of intermediate-width emission line regions ( IELRs ) in active galactic nuclei has been discussed for over two decades .
A consensus , however , is yet to be arrived at due to the lack of convincing evidence for their detection .
We present a detailed analysis of the broadband spectrophotometry of the partially obscured quasar OI 287 .
The ultraviolet intermediate-width emission lines ( IELs ) are very prominent , in high contrast to the corresponding broad emission lines ( BELs ) which are heavily suppressed by dust reddening .
Assuming that the IELR is virialized , we estimated its distance to the central black hole of \sim 2.9 pc , similar to the dust sublimation radius of \sim 1.3 pc .
Photo-ionization calculations suggest that the IELR has a hydrogen density of \sim 10 ^ { 8.8 } -10 ^ { 9.4 } ~ { } cm ^ { -3 } , within the range of values quoted for the dusty torus near the sublimation radius .
Both its inferred location and physical conditions suggest that the IELR originates from the inner surface of the dusty torus .
In the spectrum of this quasar , we identified only one narrow absorption-line system associated with the dusty material .
With the aid of photo-ionization model calculations , we found that the obscuring material might originate from an outer region of the dusty torus .
We speculate that the dusty torus , which is exposed to the central ionizing source , may produce IELs through photo-ionization processes , while also obscure BELs as a natural “ coronagraph ” .
Such a “ coronagraph ” could be found in a large number of partially obscured quasars and be a useful tool to study IELRs .