In theory, Mindef can recall every single uniform they ever issue
No, lah. No need to exaggerate that far. Ever since the SAF eMarts were introduced, I think it's more or less accepted that whatever sold inside them are considered expendable items. Those stores are supposed to serve as the modernized kit-exchange system (but without any sneering Nazi storemen ~lol~).
Previously, the expendables used to consist of stuff like foot powder, shoe polish, insect repellent, etc. (& their issuage could be quite tightly controlled by "ngeow" CQs). With them, the perennial instruction was also that, while the items wouldn't need to be strictly accountable for, they shouldn't be discarded away indiscriminately either (ala issuable disposables like toilet paper & -- if you can get them -- chinagraphs, notebooks, etc.)
I suppose camo No.4s, along with the other eMart equipment in general, are now treated the same way. You can dispose them of them on your own, but the official line is that they shouldn't end up in an unauthorized usage.
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If you browse through the relevant feedback at the Cut Waste Panel portal (see below links), you can also sense from the corresponding SAF replies that the official policy is always to equip with the latest equipment. In response to suggestions about recycling unwanted items (from reservists & the ilk), the most they're conceding is that the Army Logistics Base will accept donated stuff, & then "ALB would then decide whether to recycle or dispose the items depending on the nature and condition of the returned items."
Note the inclusive phrase "nature", cuz the present mindset is apparently also not to reuse discontinued models as much as possible (even if the items are brand-new). Presumably for a number of reasons, the most important is that we're rich enough now to afford to do this.
Then again, my reservist RQ himself used to reject discontinued models -- eg. camo No.4s (telltale color shade, as I recall), boots, jockey caps -- issued down to him for our long field exercises too, & I'm talking about the early '90s. The old items didn't look exactly hygenic, I must add. A lot of us were disgusted at the state of the Temasek Green uniforms in ROC, in particular. Used to joke was that they'd belonged to either the 1970s SAF generation or, worse yet, the 1949 Guomintang!
http://app.mof.gov.sg/cutwaste/suggestionview.asp?id=4162
http://app.mof.gov.sg/cutwaste/suggestionview.asp?id=909
http://app.mof.gov.sg/cutwaste/suggestionview.asp?id=2752
http://app.mof.gov.sg/cutwaste/suggestionview.asp?id=33815
http://app.mof.gov.sg/cutwaste/suggestionview.asp?id=28815
http://app.mof.gov.sg/cutwaste/suggestionview.asp?id=1113
http://app.mof.gov.sg/cutwaste/suggestionview.asp?id=30315
http://app.mof.gov.sg/cutwaste/suggestionview.asp?id=6971